Updated 10:58 p.m. ET, 6/3/2014
Jackson, Mississippi (CNN) - It's unclear how Tuesday's GOP Senate race in Mississippi will end, but the race has no doubt been close–and ugly–in the final stretch.
With 87% of the state's precincts reporting as of 11 p.m. ET, state Sen. Chris McDaniel was narrowly ahead of incumbent Sen. Thad Cochran, 49.9% to 48.4%, according to numbers compiled by The Associated Press.
In Iowa, CNN projects state Sen. Joni Ernst, who garnered support from Mitt Romney and Sarah Palin, will win the GOP primary for the U.S. Senate seat.
Tuesday is the biggest single day of primary voting this year, with eight states holding contests from coast to coast. But the two races that are grabbing the most attention are the contests in Mississippi and Iowa.
Tea party against the establishment in Mississippi
Cochran, 76, is hoping to win a seventh term in Congress, but he faces McDaniel, a 42-year-old conservative challenger with strong tea party support.
Cochran's supporters acknowledge the senator faces an uphill battle, but they believe he's still the best man for the job.
"There's not any doubt that Cochran is running against the current here. The political environment is perfect to upset a longtime incumbent like Cochran," Henry Barbour told CNN.
Barbour helps run Mississippi Conservatives, a pro-Cochran PAC, with his uncle, former Mississippi Gov. Haley Barbour.
But, he added, "the reason (Cochran's) going to win is he's the best candidate. He has a record of accomplishment. His opponent is a flawed candidate who's run a flawed campaign."
Cochran backers also say that if Republicans take back the Senate, the senator would become chairman of the Senate Appropriations Committee-a powerful position in Congress.
Barbour's group has spent heavily in support of the senator. Just recently it sent out anti-McDaniel fliers that look like greeting cards. When you open them up, you hear McDaniel saying what Barbour described as derogatory things from his days as a conservative radio host.
"It's just an example of some of the stupid things he's said that I think disqualifies him to represent our state," he said.
And because the Mississippi primary is open, Cochran supporters are also hoping that some Democrats show up to vote for the GOP incumbent.
CNN caught up with one such voter, Gary Gusick, who described himself as a "lifelong" Democrat who's never voted for Cochran-until Tuesday.
"I'm so concerned about McDaniel and so opposed to him that in a Republican state I think voting for Cochran is our best chance to keep McDaniel out," Gusick said, adding that "quite a few" of his Democratic friends are doing the same. "It's more important that we don't have McDaniel… than it is to cast a vote in the Democratic primary for the Democratic candidate."
But McDaniel says he feels good about his chances.
"I feel like we're going to win this thing," he said Tuesday, shortly before voting. "No doubt about it."
McDaniel points to Cochran's long career in Washington and argues Mississippi needs a new face in the nation's capital. "I think after 42 years, he's had his time."
The state senator argued that Cochran has also failed to be a representative voice for the state.
"You know, Senator Cochran has not been the conservative we asked him to be. Mississippi is a conservative state, it just doesn't fit any longer," he said. "When he went there in 1973, Richard Nixon was president. It was a different era, different time, different concerns, different worries."
"The most conservative state in the republic does need the most conservative senator," he added.
Ernst wins in Iowa
The other marquee primary Tuesday was the Republican Senate contest in Iowa. There, State Sen. Joni Ernst beat out three other GOP opponents for the nomination.
She's one of the rare GOP candidates this year who has the backing of both grassroots conservatives and the Republican establishment.
Ernst, who's also a lieutenant colonel in the Iowa National Guard and who grabbed national attention earlier this year by touting her hog castrating skills in a campaign commercial, won the support of some top names and groups among both the tea party movement and the mainstream GOP.
Related: Rubio in Iowa on eve of key primary
In Tuesday's contest, Ernst beat out businessman Mark Jacobs, former U.S. Attorney Matthew Whitaker, and conservative radio talk show host Sam Clovis.
A Des Moines Register poll released over the weekend put Ernst at 36%, 18-percentage points ahead of Jacobs, who was in second place.
Ernst will face off in the midterm elections against Democratic Rep. Bruce Braley, who faces token opposition in his party's primary. The winner of November's general election will succeed longtime Democratic Sen. Tom Harkin, who is retiring at the end of the year. Republicans feel they have a good shot at flipping Harkin's seat, in their drive to retake the Senate.
Some big names joined Ernst on the campaign trail.
"I'm honored to be here with you to tell you why it is I think Joni ought to be the next United States senator," said Mitt Romney Friday, as the 2012 GOP presidential nominee joined Ernst at two rallies in eastern Iowa. On primary eve, Sen. Marco Rubio of Florida, a potential 2016 Republican presidential contender, joined Ernst at a rally at her campaign HQ. And Rubio's Reclaim America PAC went up last week with a TV ad in support of Ernst, spending nearly $200,000 to run the spot statewide on cable TV, digital and radio.
Last week, the U.S. Chamber of Commerce, which mainly endorses mainstream Republicans, went up with a statewide ad buy in support of Ernst, who also enjoys the backing of the National Rifle Association, which also often supports establishment Republicans. The state's lieutenant governor, Kim Reynolds, has endorsed Ernst, and longtime Gov. Terry Branstad has said nice things about her, although he has not officially endorsed her.
But Ernst also enjoys the support of the Senate Conservatives Fund, which often backs conservative candidates that launch primary challenges against incumbent Republican senators. Last week it also went up with a statewide ad buy touting Ernst, who enjoys the support of the political wing of Tea Party Express, a leading national tea party group. Former Alaska Gov. Sarah Palin, still influential with many on the right, also recently campaigned with her.
Besides Rubio, two other possible 2016 GOP White House hopefuls are taking sides in the senate primary. Santorum, a 2012 Republican presidential candidate, is backing Clovis. And Texas Gov. Rick Perry, who also ran in 2012, is supporting Whitaker.
The battle for second
No one is questioning whether Democrat Jerry Brown, who's bidding for an unprecedented fourth term as California governor, is the overwhelming favorite in Tuesday's Golden State primary. The big question is whom the incumbent will face come November.
For the first time in statewide races, California is holding "open" or "jungle" primaries, in which all candidates compete in a single contest and the first and second place finishers, regardless of party affiliation, advance to the general election.
So, who will be Brown's opponent in November?
The latest polling indicates former Bush administration treasury official Neel Kashkari is slightly ahead of State Rep. Tim Donnelly for the second spot. Both are Republicans but which candidate advances to November could make a difference for the party's chances in the general election.
Some GOP strategists said they're concerned that if it's Donnelly, a conservative with tea party backing, it could hurt Republican candidates in down-ballot races in a state where the general election electorate is much more moderate than that of the GOP primary.
But wait, there's more.
One time anti-war protester Cindy Sheehan is also on the ballot, the nomine of the Peace and Freedom Party, a socialist party whose gubernatorial candidates have traditionally grabbed about 1% of the vote.
Sheehan became the face of the anti-Iraq war movement in 2005 when she protested for weeks outside then-President George W. Bush's ranch in Crawford, Texas, after her son Casey was killed in combat.
A very, very crowded primary
A new-age spiritual healer. A public radio host. A sports executive. A television producer.
Those are just four of the 16 candidates running in the primary for California's 33rd Congressional District, which includes Hollywood.
The district also contains parts of Westside Los Angeles, as well as the opulent cities of Beverly Hills, Bel Air and Brentwood. The area is losing its longtime congressman, Democrat Henry Waxman, who announced earlier this year he would retire at the end of his 20th term.
Keeping up with the celebrity endorsements and the money race in this part of the state can be a challenge. Marianne Williamson, the self-help guru, has the backing of Katy Perry and Kim Kardashian, for example.
Los Angeles City Controller Wendy Greuel and state Sen. Ted Lieu, both Democrats, are considered the most likely candidates to place in the top two and advance to the general election.
But with just as many Republicans and independents as Democrats running for the seat - and an expected low turnout - it's possible the race may not end up as an intra-party fight.
Democrat incumbent challenged in Montana
Republicans view Montana as another chance to flip a Democratic held seat in their drive to capture control of the Senate come November.
The incumbent, Democrat John Walsh, was appointed to the seat in February after longtime Sen. Max Baucus resigned to become U.S. ambassador to China.
Walsh faces two Democratic primary challengers, rancher Dirk Adams and former Lt. Gov. John Bohlinger. Walsh is considered the front-runner and political observers will watch to see how big - or how small - his margin is over his competitors. If he fails to win by a landslide, it could spell trouble in the fall.
The Democratic nominee will face the winner of the GOP race - another three-way contest - in November.
Rep. Steve Daines is considered the favorite in the GOP primary and has the support of the National Republican Senatorial Committee. He faces state Rep. Champ Edmunds and political newcomer Susan Cundiff.