The first Republican presidential caucus that counts is still months away. And though the window for new entrants will rapidly close, the field may not yet be set. Despite this, Wednesday's debate at the Reagan Library in Simi Valley, Calif., could end up defining the GOP's nomination process, as the three top contenders strategize how to get the edge over one another, and keep the rest of the candidates from taking any wind out of their sails.

Rick Perry's entry into the race has changed the entire complexion of the nomination process. Texas' longtime governor officially joined the contest just three weeks ago, but he has already vaulted to the top of the polls — in Iowa, where Michele Bachmann needs to win to have a real shot at the White House; and nationally, where Mitt Romney had previously succeeded in building some momentum as a relatively weak frontrunner. Perry will be the new kid on the block in this debate, assuming he manages to wrest himself away from his duties in Texas as wildfires rage in his state.  (As of this writing, Perry still plans to participate in the Reagan Library debate.)

Rick Perry's plan should be simple: Don't scare anyone.

The Texan's momentum puts a big target on Perry's back, of course, as his closest rivals seek to blunt his progress. Can they do it — and can they do it while looking presidential? Tim Pawlenty notoriously whiffed on a chance to attack Romney in one debate, and then got into a war of words with Bachmann in the next. Neither episode helped Pawlenty make the case that he's the conservative leader Republican voters want in this cycle. He has since dropped out altogether.

Most of the other participants need lightning to strike to capture any momentum, and most of them need lightning to strike practically everyone else on the stage, too. Only Jon Huntsman has demonstrated any momentum in the past week, offering a detailed economic plan that got an approving analysis from The Wall Street Journal. The rest of the GOP candidates have faded into the statistical noise stratum of polling, and absent a miracle, even a good performance in Wednesday's debate won't give voters much reason to seriously reconsider their candidacies.

Of the top-ranked candidates in the polls, Bachmann seemingly has the least to lose in going on the offensive. She attacked Pawlenty repeatedly on the campaign trail, and did so again in the Ames, Iowa, debate — sometimes stretching the truth to the breaking point, especially when Bachmann claimed that Pawlenty "imposed" cap-and-trade in Minnesota (the state has no such law, and Pawlenty eventually opposed a proposal to pass one) and said that he'd governed the state like Barack Obama. Bachmann did well enough at the Ames straw poll to drive Pawlenty out of the race, but she lost about 20 percent of the supporters she brought to the pay-to-vote straw poll, barely finishing ahead of Ron Paul. Within days, Bachmann started losing ground to Perry in Iowa and nationally.

Bachmann can score points on Perry for the arguable instances of crony capitalism on his record. However, she can't go overboard again like she did in Ames with Pawlenty. Perry has already proven her wrong about his track record with Texas budgets in the past week, and if she gets it wrong again, Perry will have a big opening to question Bachmann's grasp of facts and issues, a theme that has already arisen in this campaign. Still, with her numbers sinking across the board and her campaign leadership in crisis, Bachmann doesn't have much to lose, and has to stop the decline back into second-tier status.

Romney has a tougher job. So far, the former Massachusetts governor has done a masterful job of staying above the fray. Without another serious challenge from a governor in the race, all Romney needed to do as a frontrunner was to act presidential and focus his attacks on Obama. Now that recent polling shows Romney to have slipped out of pole position, he'll be tempted to attack Perry. Romney, however, isn't particularly good at being an attack dog. He'll do better at sticking to comparisons between his extensive experience in the private sector and Perry's long career in the public sector, arguing that he'd be the better thinker on job creation. Romney needs to avoid the appearance of panic at Perry's sudden ascent in the polls and act as though he still leads the race.

Perry has an easier task than it might appear. His plan should be simple: Don't scare anyone. The debate moderators will undoubtedly test the new candidate on some hot-button issues — especially evolution. Other candidates have already endured such questions in every debate thus far. Perry's response to this question and other are-you-spooky queries should be blunt and direct. No one will be voting for president in this disastrous business climate based on the candidates' views on evolution, Perry should remind viewers, and ask why the moderators aren't focusing on jobs and the economy instead. 

Perry's team and the Texas media have already set low expectations for his debate performance. Perry needs to present himself as a safe, reliable bet for Republicans in November 2012, and keep the talk on jobs. Expect Perry to take a page from Romney's playbook and act presidential, refrain from engaging the other candidates on the stage unless he has a clear opening to score political points, and to focus all of his attacks on Obama.

Polling suggests that the nomination race has become Perry's to lose. If he turns in at least a serviceable performance Wednesday, eliminating the notion that Perry is too scary to put on the national ticket, this might transform into a two-man race. If Perry bungles it, the race will once again become wide open. Given the obvious dissatisfaction with the rest of the field among Republican primary voters that Perry's rapid rise has shown, that will act as a powerful draw to potential high-profile candidates.