DES MOINES, Iowa -- Eight candidates will take the stage in Ames, Iowa tonight in the second major presidential debate of the 2012 race, an event that amounts to a kickoff off one of the busiest — and most important — weekends in the contest to date.

We’ll be in Ames live-blogging the proceedings, which get started at 9 pm eastern time, but with hours to kill before the debate starts we thought we would provide a bit of a primer on what to watch for tonight.

* Target Bachmann: In the two months since the candidates last shared a stage, Minnesota Rep. Michele Bachmann has surged into the top tier and is widely regarded as the frontrunner in the Ames Straw Poll on Saturday. That’s a mixed blessing for Bachmann who will not only have to meet or exceed high expectations for her in tonight’s debate but will also have to do so while likely dodging barbs aimed at her from the likes of former Minnesota governor Tim Pawlenty and others. How Bachmann handles the attacks — if and when they come — will almost certainly be a major storyline coming out of Ames tonight. Running from the front is a major challenge and one Bachmann isn’t terribly familiar with; she needs to be a fast learner.

* No more Mr. Nice Guy: Pawlenty ducked a chance to attack former Massachusetts governor Mitt Romney at the debate in June and it cost him; his campaign went into a free-fall that he has struggled to turn around since. Pawlenty desperately needs to show signs of life in advance of the Ames Straw Poll, which amounts to a make or break moment for his campaign. The best (only?) way for him to do that is to, as our Post colleague Amy Gardner put it, come out swinging. The most obvious target for Pawlenty is Bachmann who is running ahead of him in Iowa and who has largely eclipsed him in recent months. But, attacking a woman — and the only woman on stage — in a debate setting is a dangerous game for Pawlenty that must be carefully considered. Perhaps Pawlenty bypasses a direct Bachmann attack — due to the peril associated with it — and tries to make up for lost time by slamming Romney, the race’s frontrunner. What Pawlenty must avoid is coming across as simply swinging wildly in all directions in hopes of landing a verbal blow. That would reek of desperation, which is a not a scent often associated with winners.

* In absentia: In addition to the eight men and women on the stage tonight there will be two people standing just off camera (figuratively, not literally): Texas Gov. Rick Perry and former Alaska governor Sarah Palin. Palin is rumored to be making a trip to the state tomorrow to attend the state fair (and trample on the attempts by her potential rivals to draw media coverage). Perry will stop in Iowa on Sunday, 24 hours or so after making clear his plans to run for president with stops in South Carolina and New Hampshire. CNN polling released today shows Perry and Palin running relatively strong in a national primary matchup against the current field so it’s easy to imagine that the debate moderators may well ask those on stage about the two people who still aren’t. None of the candidates — if they’re smart — will engage in handicapping the bids of people not there. But, it the field comes across as small or not particularly dynamic tonight, it gives the likes of Perry and.or Palin to step in and fill that charisma void.

* Fresh faced appeal?: Former Utah governor Jon Huntsman will be the new face on the debate stage tonight as he is the only one of the eight candidates who did not attend the New Hampshire debate in June. Since announcing his candidacy eight days after that debate, Huntsman has struggled to carve out space for himself in the race. Is he the practical-minded moderate? A conservative problem solver? The nice guy? An attack dog? This is Huntsman’s best chance to sharpen some of the lines of his candidacy for voters who still have little to no sense of him after two months in the race.

* How do you solve a problem like Ron Paul?: In presidential debates over the past four years, the candidates sharing a stage with the Texas Congressman have largely ignored him as he champions his libertarian views on the role of government both at home and abroad. But, Paul is a legitimate contender in the Ames Straw Poll and other recent surveys suggest his following has grown from four years ago. Engaging Paul still seems like a no-win situation for any of the top tier candidates but ignoring him entirely allows him to build momentum among his fervent supporters for the straw poll. Paul still feels like a niche candidate to us — see our piece on what he has in common with “Friday Night Lights” — but he is clearly a larger factor heading into the Ames Straw Poll than most people thought he would be.

* Rick the wildcard: We’ve written before that former Pennsylvania senator Rick Santorum has no qualms about going after his rivals — often right to their faces. With Santorum, like Pawlenty, needing to show some signs of life at the straw poll, he may well lead the attacks against Bachmann and/or Romney, giving others the chance to pile on. In the New Hampshire debate, Santorum was quite good but that storyline was pushed off the radar screen because of Bachmann’s star turn. Santorum knows it may be now or never for him in the race and is likely to be willing to take some chances tonight. And that makes him someone to keep an eye on.

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