Texas Gov. Rick Perry didn’t get walloped in the Reagan Library debate; but in the days following that he’s lost the spin war and some momentum. Ever since the debate, his stance and rhetoric on Social Security have dominated the discussion. Mitt Romney is knocking him about the ears. Rep. Michele Bachmann (R-Minn.) is planning on taking him on. And a college kid from Virginia’s George Mason University who wants to start an anti-Perry PAC sent out an e-mail Sunday that read in part:

America Cannot Afford Rick Perry is an unaligned watchdog organization that seeks to educate the public about political figures seeking our nation’s highest office. His intemperate language and clear deficiencies in policy arguments will severely weaken the GOP’s ability to reclaim the White House in 2012. As an career politician, holding elected office since 1984, Rick Perry doesn’t understand the economy and its relationship with our federal government. And at this time in our nation’s history, the Republican primary voters are longing for a leader who can not only defeat President Obama, but enact structural changes to some of our largest social welfare programs in order to restore solvency-- medicaid, medicare, and social security. However, Governor Perry has taken an extreme stand on these social welfare programs that are anathema to Primary and General election voters. Herein lies our issue with Governor Perry — his hypocrisy. While Governor Perry frequently castigates the federal government for acting “unconstitutionally” and “over-reaching,” he seems to be unaware that Texas has benefited greatly from this same federal government — namely in the form of stimulus funds to balance Texas’ budget as well as border patrol agents who temper the flow of illegal immigrants.

Yikes. The debate tonight should have plenty of fireworks.

Perry has several challenges. First, he’s got to short-circuit the Social Security debate, and other potential potholes, by stepping away from his past incendiary language, including some of the ideas he offered in his book. That’s not easy, and he may not even want to do it. But if he allows his opponents to paint him as a Ron Paul-like loose cannon, Republicans will begin to doubt his viability. It would also help for him to begin to put meat on the bones — that is, explain what he would do as president rather than simply recite his record in Texas and criticize the president.

Romney’s challenge is different. A GOP operative tells me, “Perry needs to put to rest questions about whether or not he has a command of the issues while Romney needs to keep the focus on the economy and hope that Perry trips himself up.” Moreover, he’ll need to show some zest for conservative principles, making clear, for example, that he’s against government picking winners and losers (a criticism that applies to both the president and Perry) and for tax and entitlement reform. A Capitol Hill Republican e-mailed me on Sunday, “It’d be great if he went after fixing our entitlement problem as aggressively as he’s going after those talking about our entitlement problem.” Indeed.

In the Romney-Perry duel tone also matters. Perry can’t lose his cool or appear annoyed with questions about his views. That won’t go over well in early primary states that expect to grill the candidates. Romney, on the other hand, could use some righteous indignation from time to time. (Why, for example, is Perry’s camp criticizing his Bain experience — don’t they like capitalism?)

As for Bachmann, the stakes could not be higher. If Perry falters, she’s currently the best positioned to reclaim support from Tea Partyers and social conservatives. She, too, will have to go after Perry’s language on Social Security and challenge him on grounds of crony capitalism (his high-cost lifestyle charged to taxpayers, his appointment of pals to boards and his tech funds that seem to mirror the Solyndra-style of business development). She’s got the conservative bona fides to contest his positions on HPV, gay marriage and immigration from the right. Her biggest problem will be to prevent the debate — and the race — from becoming a two-man contest between Romney and Perry.

The sleeper in this debate and in the race may be Rick Santorum. Like Bachmann, he has been hampered by moderators who treat him as an afterthought. One way to get into the mix, of course, is to begin calling out the other candidates. Why hasn’t Perry mentioned Iran once in this campaign and why did he flip-flop on the 10th Amendment? Why does Jon Huntsman want to surrender in the war against jihadists? What kind of Republican favors mandates — to buy insurance or to require girls to get HPV shots? Perry is entirely capable of winning some of these face-offs, but he has to make the most of brief opportunities he is given.

No single debate is do or die, but over time impressions of the candidates will harden. Perry wants to avoid being tagged as the know-nothing hothead. Romney wants to convince conservatives he is one of them. Bachmann wants to dispel the notion she is an also-ran. And Santorum wants to climb into the thick of things where he can make the case he’s a principled conservative with both national security and entitlement reform experience. Whoever can make the most headway on his or her particular challenge will get some momentum to take into the debates that follow.