Updated 3:03 p.m. ET

Republicans hoping to defeat President Obama meet tonight in the first of several debates over the next few weeks that could help shape the 2012 race.

If wildfires in Texas don't cause a change in his plans, Rick Perry will meet his GOP rivals in a face-to-face matchup for the first time since he joined -- and shook up -- the race Aug. 13.

Perry, the Texas governor, sits atop Gallup and other national polls for the GOP nomination. He's been followed in those polls by Mitt Romney, a former Massachusetts governor making his second White House bid, and Sarah Palin, the 2008 GOP vice presidential nominee who has not declared her intentions.

Palin won't be on the stage at the Ronald Reagan Presidential Library tonight, but eight candidates will debate at 8 p.m. ET on MSNBC. The debate is sponsored by Politico and NBC News.

Here are five things to watch and some questions posed by USA TODAY readers:

1) How will Rick Perry perform in his national debut?

This is a chance for the Texas governor to introduce himself to a national audience, and he's sure to get attacked by his opponents. Texas Rep. Ron Paul and a group supporting Minnesota Rep. Michele Bachmann have gone after Perry directly.

Perry, the longest-serving Texas governor, will probably bring up his record of creating jobs in the Lone Star state. Two ex-governors in the debate, Mitt Romney and Jon Huntsman, have recently outlined their economic plans and have been eager to claim the mantle as the top job creator.

Perry "needs to try to appear relatively calm and resolute but give an energetic description of his views," says Cal Jillson, a political scientist at Southern Methodist University in Dallas.

Jillson recommends that Perry avoid one-liners that have attracted attention, such as his statement at a South Carolina forum that his position on gun control is to "use both hands."

"In Texas, that's entertainment, but in the rest of the country, that puts people's nerves on edge and fuels doubts," Jillson says.

2) Can Mitt Romney make his case and reclaim ground lost to Perry?

In two previous debates, Romney was at the top of the national polls for the nomination and was largely untouched by his rivals during those faceoffs. Perry has eclipsed Romney in eight national polls since joining the race.

"He has to do something to enthuse the core Republican base voter," says Mark Rozell, a professor of public policy at George Mason University in Fairfax, Va. "One new candidate jumps into the race, and it knocks him out. That shows a real weakness to his candidacy."

GOP pollster Kellyanne Conway says Romney needs to make his case that he's the best alternative to Obama.

"Romney should confront straight on this idea that he's 'not conservative' enough by looking into the camera and saying the current president is too liberal ... and too destructive to the nation," says Conway, CEO and president of the polling company inc./Woman Trend.

"Take the case directly to Obama and reaffirm in first person: I am pro-life, I am conservative," she says.

3) Will Michele Bachmann get back her momentum?

Bachmann's momentum after her victory in the Iowa straw poll was short-lived because of Perry's entrance into the race. Her first debate performance in New Hampshire helped Bachmann establish herself in the campaign and vaulted her to the top of public opinion polls in Iowa, home to the first presidential caucuses.

The founder of the House Tea Party Caucus, Bachmann finds herself battling with Perry and Romney for supporters of the small-government, anti-tax movement. A recent Gallup Poll showed Perry leads Bachmann and Romney by 21 percentage points among Tea Party supporters.

"Michele Bachmann needs to prove that she's more than Rick Perry's warmup act. She has to stand out in some way, which is tough because their positions are so similar," says John Pitney, a political scientist at Claremont McKenna College near Los Angeles.

4) Can Jon Huntsman go on the attack and gain ground?

Huntsman, most recently U.S. ambassador to China, has increasingly sharpened his attacks against Romney and Perry. He criticized Romney's jobs plan as "sadly similar to that of Obama's" and made an issue of Perry's beliefs on evolution and climate change.

This is Huntsman's chance to define himself by showing how he is different from his rivals and to make his case to a national audience. He averages 1.3% in national polls on the race, according to RealClearPolitics.

How Huntsman does this will be important. "In a more gentlemanly way, Huntsman is likely to draw real contrasts," Jillson says. "What Huntsman wants to do is appeal to moderates -- a fairly small slice in the Republican Party -- and beyond."

5) What will Ron Paul, Newt Gingrich, Herman Cain and Rick Santorum do?

Paul, the Texas congressman with libertarian views, has a strong following and finished a close second to Bachmann in the Iowa straw poll. In a new ad, he notes his support of Reagan in 1980 and takes on Perry.

Paul has done better than Gingrich, Cain and Santorum in Gallup and other national polls but is well behind Perry in those surveys. Jesse Benton, Paul's campaign manager, was disappointed by the lack of media coverage of the Texas congressman after the Iowa straw poll.

Gingrich, the former House speaker; Cain, ex-CEO of Godfather's Pizza; and Santorum, a former Pennsylvania senator, have had trouble breaking through in the campaign.

Some USA TODAY readers have weighed in with questions they'd like to hear answered in the debate:

Jorma Larton wants to know about the candidates' religious beliefs and how they would affect the Republicans if they're elected to the White House.

"What would you specifically do to reduce the size of the federal government and the deficit?" asks reader Dick Edmunds.

"What would you do to reign in the federal government and return it to the principle activities outlined in the Constitution?" Frank Rice asks.

Check back in USA TODAY's On Politics for live coverage of the debate. The next debate will be held Sept. 12 in Florida and will be co-sponsored by the Tea Party Express and CNN.