(CNN) - Former President Bill Clinton will lend his star power to the Senate race in Arizona when he campaigns for Democratic former U.S. Surgeon General Richard Carmona at a rally Wednesday night.
Clinton's appearance at the rally at Arizona State University could be another sign that the Democrats think they could take the Senate seat in the final month of the election.
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A number of partisan polls - both Republican and Democrat - in the last month show a tight race between Carmona and six-term Congressman Jeff Flake.
Recently, the Cook Political Report moved the race from “leans Republican” to a toss-up race, while the Rothenberg Political Report maintained the races as “toss-up/tilt Republican.”
And last week, the Democratic National Senatorial Committee announced a $526,000 weeklong ad buy in Arizona, the Washington Post reported.
Not to be outmatched, Club for Growth, a leading fiscal conservative group, pumped $500,000 into ads in Arizona last week.
The Club for Growth ad asked Arizona voters, “Do you know that a vote for Carmona is a vote to put liberals in charge of the U.S. Senate?"
With one-third of the Senate’s seats up for election in 2012 – and about a third of those are hotly contested - each seat won by either party could tip the balance of power.
The DSCC countered with a buy that brought their two-week total to over $1 million.
Clinton, who ended his two-term presidency with a 66% approval rating, according to a Gallup poll, has been a valuable asset to Democratic campaigns – both Congressional and presidential.
Following a well-received speech at the Democratic National Convention last month, Clinton’s appearance for Carmona this week could also help the Obama campaign in the Grand Canyon State.
That’s because the state that five-term Arizona Sen. John McCain carried by more than 8 points during his 2008 presidential bid is also in play for Democrats in the presidential election.
Arizona’s 11 Electoral College votes are labeled "leaning Romney" on the CNN Electoral Map. Key members of the Obama campaign, including Vice President Joe Biden, have indicated they think Arizona is up for grabs.
"We think we have a real shot at winning the presidential race here in Arizona," Biden said at a campaign event in Arizona in April.
Obama senior adviser David Axelrod signaled the campaign was looking to sway leaning states during an appearance on CNN's “State of the Union” last Sunday.
"We are always looking, always looking for opportunities, and, you know, we’re heartened by what we see, not just in these battleground states, but some of the states that weren’t battleground states,” Axelrod said when asked about campaign activity in Arizona.
Arizona has only voted for one Democratic presidential candidate in 60 years.
Before heading to Arizona, Clinton will join President Barack Obama Sunday in Los Angeles at a private fundraiser and then campaign alone for the president in Las Vegas on Tuesday.
- CNN’s Kevin Bohn and Kevin Liptak contributed to this report