You've got to feel a bit sorry for Mitt Romney. The guy has been running for president since 2006, earning at best a tepid reception from the Republican electorate - and along comes rootin' tootin' Rick Perry, who gallops into the polling lead after being in the race for maybe five minutes.

Romney figured originally that he could cruise above the fray as various second-tier right-wingers (Bachmann, Santorum, Cain, Paul, Gingrich) knocked each other off, thereby clearing the way for his nomination. Perry has upended that scenario. He is Romney's worst nightmare - an earthy, unvarnished conservative who excites the base, a rival financed for the long haul by a broad swath of well-heeled anonymous donors.

So, Romney clearly needs to alter the new dynamic, and suggest (if only indirectly) that Perry is too extreme to win a general election. In fact, it'll be instructive to see whether he saddles up tonight, when Perry is standing just a few feet away. The Republican candidates are back on stage for another debate, and Perry is slated to join the fun for the first time.

Romney is in a bind. If he leaves Perry untouched, he risks looking weak; voters respect candidates who fight. If he shrinks from challenging Perry's credentials, he risks falling farther behind. On the other hand, if he does confront Perry, he risks redefining the race as a one-on-one with the Texas governor - a potentially perilous scenario, given the fact that Perry is widely considered to be the superior gut-fighting retail politician. If Romney assails Perry's extremism, conservative primary voters might simply train their ire on Romney, faulting him for soiling their new hero. Romney hardly wants to risk a conservative backlash during the run-up to Iowa and South Carolina, where conservatives dominate the Republican voting.

The thing is, Romney has great material to work with, and calling out Perry would be the responsible course of action. Romney's people are well aware, for instance, that Perry's 2010 book "Fed Up!" is a veritable treasure trove - to wit, the Perry assertion that Social Security is "unconstitutional" and that "by any measure, Social Security is a failure."

Really? "By any measure" Social Security fails? No wonder Karl Rove believes that attacking the book is a slam dunk. If Romney has even an ounce of guts, he should be comfortable pointing out that, whatever the program's current financial straits, it has long provided a floor of support for seniors, injured workers, widows, widowers, children who lose a working parent, and millions of others. Romney's chief challenge - now amplified by Perry's presence in the race - is to persuasively argue that conservatism can and should co-exist with the reality that Washington is not always the arch enemy of the common man.

Romney needs to say, in effect, "I'm the responsible conservative; he's the reckless conservative." How reckless? Perry wants to repeal the 17th amendment to the U.S. Constitution, which gave voters the power to elect U.S. senators. How hard would it be for Romney to suggest that it's nutcase thinking to want to return that power to the state legislators? Yes, some tea partyers inexplicably say yes to repeal, but I bet that your typical mainstream voter would not.

In short, Romney needs to make a strong electability argument, and suggest, starting tonight and if only by inference, that a conservative who's bent on turning back the clock 100 years has no chance of beating a vulnerable Barack Obama. But if Romney isn't willing to play hardball, if he lacks the smarts and the moxie to favorably define himself at Perry's expense, he's probably doomed. And deservedly so.

It's likely, of course, that Romney will punt on this opportunity tonight, that instead he will bang away on Obama's economic stewardship. Romney will likely allude to Perry in only the most veiled fashion (perhaps by repeating his recent complaint about "career politicians," a glancing reference to Perry's 10-year gubernatorial tenure), and he'll likely let the second-tier candidates lead the anti-Perry assault. Bachmann needs to take some shots, because, among conservative voters, Perry is eating her lunch; and Santorum is desperate for somebody, anybody, to pay him some attention. As for Jon Huntsman (R-Sanity), he might target Perry, but the word today is that he has a sinus infection and can barely talk.

All told, Romney may no longer have the luxury of disengagement. Even though his aides reportedly insisted in late August that the attacks on Perry will begin "at a time of our choosing," it doesn't appear that time is on Romney's side.

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