(CNN) - Voting is underway in Michigan and Arizona Tuesday where the top four Republican presidential candidates, Mitt Romney, Rick Santorum, Newt Gingrich and Ron Paul are competing to capture the state's delegates. It is largely a race between Romney and Santorum for the top spot in the former's native state of Michigan, while Romney has maintained the top spot in polling leading up to Arizona's primary.
Wins in Tuesday's states would provide welcome momentum ahead of Saturday's contest in Washington and in the 10 states set to vote on Super Tuesday, March 6. Check back below for news from our reporters and producers and tune in to CNN throughout the night for live coverage. Read more here.
11:20 p.m. ET - @AriFleischer: Super Tue. look ahead: Rom wins VT, MA & VA. Paul wins caucuses in AK, ND, & ID. That means 4state fight in GA, OH, TN, & OK.
11:04 p.m. ET - @davidaxelrod: Two weeks of intensive campaigning in MI, and less than half said they strongly backed their choice. Can't wait until they get to Ohio!
11:03 p.m. ET - @crowleyCNN: MR's post speech grip and grin continues. He's the one in the back in the dark suit. twitpic.com/8q1e4q
10:58 p.m. ET - Santorum told @jimacostacnn after his remarks that he will not recalibrate his message following the results Tuesday.
"I think that's a pretty good message, the message I’ve been giving," Santorum said. "And obviously it did very very well in Michigan."
Santorum said Tuesday was going to be "Romney's night," but the question was how big.
"And it wasn't very big ... It's a two man race now, that's pretty clear," Santorum said.
10:55 p.m. ET - @crowleyCNN: MR still in election night ballroom shaking hands. This may be a record linger
10:54 p.m. ET - @David_Gergen: Did Romney finally capture in few words the essence of his campaign pledge? "More jobs, less debt and smaller government!" #CNNElections
10:53 p.m. ET - @DWSTweets: Romney's run to the right may have allowed him to stumble forward in the slog for the GOP nomination—but it has hurt him irreparably.
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10:52 p.m. ET - @ErinBurnett: Mitt seemed to find a rhythm in his speech tonight. Lots of one liners. But his wife was the standout as usual. #cnnelections
10:49 p.m. ET - @DanaBashCNN: Takeaway: dems mischief to try to slow romney momentum and embarrass him in his homestate didn't work #cnnelections
10:42 p.m. ET - @crowleyCNN: MR: " If there's one thing we can't afford it's four more years of Barack Obama with nothing to answer to. "
10:37 p.m. ET - @crowleyCNN: MR " We didn't win by a lot but we won by enough and that's all that counts".
10:36 p.m. ET - Romney said one of the positive aspects of having a big family is the ability to dispatch them to different states. Two of his sons are in Arizona with Romney backers Arizona Sen. John McCain and Arizona Gov. Jan Brewer, who he thanked for their tireless support.
10:33 p.m. ET - Ann Romney's typical thank you introduction to her husband at his campaign headquarters in Novi, Michigan included a shout out to Donald Trump and Kid Rock.
10:30 p.m. ET - @crowleyCNN: That breeze you feel? Small sigh of relief from GOP establishment pending Ohio. Stand by for SOD ( son of Detroit)
10:23 p.m. ET - @donnabrazile: Sorry Mr. Santorum, one speech will not correct the damage done to your candidacy or to women across America who will never trust you ever.
10:20 p.m. ET - @jimacostacnn: Santorum talking about "how well we did" in Michigan. Basically a concession. #CNNElections
10:19 p.m. ET - With 71% of precincts reporting, Romney received 41% of the vote, followed by Santorum's 37%, Paul's 12% and Gingrich's 7%. While Romney won the popular vote, CNN has not yet projected whether Romney or Santorum will win the most delegates.
10:17 p.m. ET - Romney won the Michigan primary, CNN projected based on exit polling and the actual vote in the state.
10:16 p.m. ET - @DanaBashCNN: Source tells me rick santorum called romney to concede #cnnelections
10:15 p.m. ET - @AriFleischer: This is called trying to make up for the statements Santo made earlier that hurt him with women...
10:12 p.m. ET - Santorum paid tribute to his 93-year-old mother, who he said was ahead of her time as a working mother and taught him how to balance work and family. He said her strength is the reason he married his wife Karen. Describing the start of their relationship, when he hired her at his law firm, Santorum said he "recruited her in more ways than one."
10:10 p.m. ET - "A month ago they didn't know who we are but they do now," Santorum told supporters in Grand Rapids, Michigan.
10:06 p.m. ET - @crowleyCNN: Michigan AG says people call MItt "son of Michigan" but he will call him "Prez of the US" Counting chickens while they r still yolks?
10:05 p.m. ET - Although Gov. Snyder said he is a proponent of the open primary system, he was critical of those using their votes to help Obama in the general election.
"That's not a great use of democracy," Snyder said.
10:03 p.m. ET - Republican Michigan Gov. Rick Snyder, a Romney supporter, said he expects him to win in the state Tuesday.
In an interview with @crowleyCNN, Snyder said the general election should focus on the future instead of the past, like the auto bailouts.
10:01 p.m. ET - @David_Gergen: Looks like Romney will win MI –two big ones that will help right his ship ... But rough waters still ahead. #CNNElections
9:59 p.m. ET - @PeterHambyCNN: Romney folks are very peppy right now. Basically just waiting for the race to be called at this point so he can speak.
9:45 p.m. ET - @adamplevycnn: Santorum now takes the #2 del spot. Current est: Rom 159, Sant 40, Ging 38, Paul 27. Updates all night: tinyurl.com/794v55f #CNNElections
9:40 p.m. ET - @DanaBashCNN: just went live at the oakland county election center with "first on cnn" numbers. now: 76% reporting 49% romney 31% santorum #cnnelections
9:34 p.m. ET - @alexcast: romney is paying the price for opposing bailout. he hasn't tried to reap benefit: he demonstrated strength and spoke truth to power
9:30 p.m. ET - @PeterHambyCNN: No matter who wins Michigan tonight, big mo unlikely for Super Tuesday. Geography tough for every candidate. Race will move on after that.
9:27 p.m. ET - When asked how he will try to win the contest in Virginia, Paul told CNN's Wolf Blitzer that his "message is the same no matter where I go."
9:22 p.m. ET - Appearing on CNN, Paul said "there's no truth" to a suggestion from Santorum he is abstaining from criticism of Romney to help the former Massachusetts governor's candidacy.
"If that's all he has to talk about that means he doesn't have much of a platform," Paul said of Santorum. "He just pulled that out of the air because there's no truth to it."
9:16 p.m. ET - With 28% of precincts reporting in Michigan, Romney received 41% support, followed by Santorum with 38%, Paul with 11% and Gingrich with 7%.
9:08 p.m. ET - @LisaDCNN: MICHIGAN TURNS: Romney overtakes Santorum for 1st time. Romney 41%, Santorum 38%, with 20% reporting.
9:06 p.m. ET - Forty-eight percent of voters surveyed in CNN exit polling said the economy was the top issue for them in the 2012 campaign. Thirty-two percent of respondents said it was the budget deficit. Twelve percent listed illegal immigration as their top issue and 6% said abortion.
9:04 p.m. ET - @PrestonCNN: Unlike Mich. where the delegates are divided proportionally, in Ariz. 2nd, 3rd, 4th place receive the same # of delegates: 0
9:03 p.m. ET - @DanaBashCNN: I'm Inside the command center in oakland county – romney country. now at 37 percent reporting romney 19500 santorum 13600 #cnnelections
9:02 p.m. ET - With 19% of precincts reporting in Arizona, Romney received 41% support, followed by Santorum's 39%, Paul's 11% and Gingrich's 7%.
9:01 p.m. ET - CNN exit polling in Arizona showed Romney with 44% support followed by Santorum with 27%, Gingrich with 16% and Paul with 11%.
9:00 p.m. ET - Mitt Romney won the Arizona Republican primary, CNN projected based on CNN exit polling.
8:49 p.m. ET - @LisaDCNN: MICHIGAN – IT'S CLOSE: 10% reporting. Santorum – 40%, Romney – 39%. Under 800 votes (out of 86K) separate them now.
8:40 a.m. ET - Paul addressed supporters in Springfield, Virginia and criticized the actions of the Federal Reserve, a constant theme for the Texas representative.
8:39 a.m. ET - @alexcast: next week gets tougher for mitt. super tues not an establishment day. ohio is mich w/out the romney family history. #cnnelections
8:26 p.m. ET - @LisaDCNN: ROMNEY HOMESTEAD – HO HUM?: Oakland County, where Romney grew up, is only 38% Romney, 37% Santorum. But those are v. early #s.
8:22 p.m. ET - @David_Gergen: Romney says he likes tree heights in MI. Newt tells endless story re cutting a tree. What is it with these guys and trees? #CNNElections
8:20 p.m. ET - @crowleyCNN: Do we think the Supremes " Where Did Our Love Go" is the best choice for music in Romney's Michigan election night ballroom?
8:19 p.m. ET - With 1% of precincts reporting in Michigan, Santorum leads with 41%, followed by Romney's 36%, Paul's 12% and Gingrich's 8%.
8:17 p.m. ET - @DanaBashCNN: Is this newt's attempt to overcome the "angry" candidate rep? Where are we going w/ this? #cnnelections
8:12 p.m. ET - @DLoesch: This sounds like an "I'm giving up speech."
8:11 p.m. ET - Gingrich spoke at the University of West Georgia, where he once taught. He said he was reminded of his age when he approached the stage. He was greeted by individuals who said their parents were his students.
8:07 p.m. ET - Callista Gingrich introduced her husband at his campaign headquarters in Carrollton, Georgia.
7:56 p.m. ET - @jimacostacnn: More Brabender on poss. late entrant: "not in the best interest of this party... big mistake if that were to happen."
7:55 p.m. ET - @jimacostacnn: Asked Santorum's Brabender on poss late entrant: “This is not about having a relief pitcher come in who is fresh from the bullpen..." 1/2
7:47 p.m. ET - @KateBolduan: Excited crowd at Ron Paul rally in Virginia tonight. Waiting for the congressman and primary results yfrog.com/h0ihwbsj
7:46 p.m. ET - @Jon2012girls: Can someone light their hair on fire already and get this GOP race over with. #whatstakingsolong?
7:38 p.m. ET - @crowleyCNN: Book? Candidate stays @CIA. Press on plane think they flying 2 different cities,but only circling while CIA changes road signs& hotel pho#s
7:25 p.m. ET - @SamFeistCNN: Could the Dem. Mischief make a difference? Watch Wayne County. Could help Santorum win delegates in CD 12-13. #CNNelections
7:14 p.m. ET - @PaulBegala: Can anyone recall another candidate having as much trouble in a home state primary as Romney's having in MI? I can't.
7:12 p.m. ET - @AriFleischer: Parties allow crossover voting in an effort to grow the party & attract new people. That's why there are open primaries.
7:11 p.m. ET - @AriFleischer: Turnout in 2008 in MI was 868,818. I suspect tonight will be less than that – and that's not a good sign for my team.
7:10 p.m. ET - CNN exit polling showed 53% of Michigan primary voters were tea part supporters compared with 28% who said they were neutral toward the grassroots movement and 17% who opposed it. Sixty-two percent of voters said they did not consider themselves Evangelical Christians, while 38% said they did.
7:01 p.m. ET - @AriFleischer: In the 2000 MI primary between Bush-McCain, only 48% of voters were Rs, 35% Indy, 17% D. Bush lost to McCain.
7:00 p.m. ET - In Arizona, almost 364,000 votes were already cast, according to Arizona county election offices. In Michigan, over 219,000 voters were already cast, according to the Michigan Secretary of State's office.
6:54 p.m. ET - @AriFleischer: Exits show last debate hurt Santo. For those who said the debate was a factor, they voted R 39, S 36. Not a factor R 37, S 44
6:51 p.m. ET - @AriFleischer: Looks like 10% of the voters in the MI primary are Dems, up from 7% in 2008, down from 17% in 2000. Not a big deal if u ask me
6:45 p.m. ET - @PaulBegala: Only 10% of voters in MI are Dems – down from 17% in 2000. Hardly "raiding" or "mischief." Big news: Romney is SO weak in his home state.
6:38 p.m. ET - The Republican presidential candidates have opposed the auto bailout on the trail, but 43% of voters in Michigan's primary voters said they approved of the bailout, while 51% said they did not, according to CNN exit polling. Fifty-four percent of those questioned said the economy was the top issue in the 2012 campaign.
6:28 p.m. ET - @DanaBashCNN interviewed a Michigan voter who considers himself a Democrat but voted for Santorum, who he said would be the least competitive candidate against President Barack Obama in 2012. How did he feel after he voted? "A little dirty ... went home and showered," he replied.
6:20 p.m. ET - @adamplevycnn: Santorum could surpass Gingrich and take the #2 delegate spot tonight. Current estimate has Gingrich up by 1. #CNNElections
6:18 p.m. ET - @AriFleischer: Get ready to stay up late. Michigan is going to be close...
6:17 p.m. ET - @piersmorgan: BREAKING NEWS: @THEHermainCain has been speaking FRENCH on British TV tonight. Zut alors! @BBCNewsnight
6:16 p.m. ET - @crowleyCNN: 3/28/12 All my life's a circle twitpic.com/8py2e7
6:15 p.m. ET - Romney won a plurality (34%) of voters who said the economy was "not good" or poor" in the 2008 GOP contest in Michigan. Those voters represented 68% of the Republican primary vote. He also carried the majority of Republican voters who described themselves as conservatives with 41% support to McCain's 23%.
6:11 p.m. ET - Romney was raised in Michigan where his father, George, was a three-term governor. Forty-two percent of GOP primary voters in 2008 said his ties to the Wolverine State were important to them.
6:09 p.m. ET - Romney was victorious in the 2008 Michigan contest with 38.9% of the vote to McCain's 29.7%, Huckabee's 16.1% and Paul's 6.3%.
6:05 p.m. ET - Thirty percent of Michigan voters described themselves as "very conservative," while 30% said "somewhat conservative" and 40% said "moderate" or "liberal," according to CNN exit polling. Fifty-nine percent identified themselves as Republicans, while 10% considered themselves Democrats and 31% as independents.
6:04 p.m. ET - – Mormons represented 11% of the Arizona GOP primary vote in 2008, 88% of whom voted for Romney, who is a member of the Church of Latter-day Saints.
6:03 p.m. ET - – Sen. John McCain of Arizona won the 2008 Arizona GOP primary with 47.2% of the vote, followed by Romney's 34.5%, Mike Huckabee's 9% and Paul's 4.2%. In the same year, Romney beat McCain among self-described "moderate" and "somewhat conservative" Republicans, who represented 62% of the Republican primary vote at the time.
5:02 p.m. ET - Gingrich said the U.S. has no "longterm obligation in Afghanistan or Pakistan."
"[We] don't have to go around appeasing corrupt governments," Gingrich said after saying America could shift its energies instead to countries like India.
4:57 p.m. ET - Looking forward to Super Tuesday, Gingrich told CNN's Wolf Blitzer he must win his home state of Georgia on March 6 and expects to pick up delegates in the other states.
4:53 p.m. ET - Appearing on CNN, Gingrich said Romney has "more at stake" in the Michigan primary. If he loses his home state, it is "hard to understand the rationale for his campaign," Gingrich said.
The former House speaker said Romney's campaign was based on the assumption that he was the inevitable GOP nominee, and that is a more difficult position to take if he loses Michigan.
If Santorum loses, there will be "doubts about whether he can go the distance," Gingrich added.
4:51 p.m. ET - @DanaBashCNN: Reporting tonight from bloomfield hills, michigan – where romney went to elementary & hs. He should do extremely well here. If he doesn't...
4:27 p.m. ET - @deirdrewalshcnn: On day of MI/AZ primaries @RonPaul in DC at the Capitol, voting now on House floor on amendments to education bill
4:12 p.m. ET - @jimacostacnn: Hanging "made in America" banner at Santorum HQ. A sign he's ready to pivot to economic issues for Super Tuesday. pic.twitter.com/3ZE6NrgN
3:23 p.m. ET - @miguelmarquez: Early ballots being counted in Phx. We r in the heart of democracy in AZ pic.twitter.com/ni547MKm
2:23 p.m. ET - @KevinBohnCNN reports the Michigan Secretary of State's office estimated turnout for the primary to be between 15% and 20%, compared to the 21% in 2008. The office said 243,575 people requested Republican ballots and 219,153 of those were returned.
Arizona Nuts and Bolts:
– Polls open: 8 a.m. ET – 9 p.m. ET
– Closed primary: Only registered Republicans may participate in the primary
– Delegates at stake: 29
– Allocation rule: Winner-take-all
– Arizona registered voters (as of 1/1/12): 3,542,606
– Arizona registered Republicans (as of 1/1/12): 1,219,424
Michigan Nuts and Bolts:
– Polls open: 7 a.m. ET – 9 p.m. ET
– Open primary: Voters do not register by party. Any registered voter may participate in the GOP primary
– Delegates at stake: 30
– Allocation rule: Proportional to statewide vote with 15% threshold
– Michigan registered voters (as of 10/17/11): 7,267,348