At first blush, Newt Gingrich appears to be the antithesis of the Tea Party. The former Republican House speaker has spent decades inside the Beltway as a brilliant political operative, in and out of office. He has worked with Democrats to achieve compromises that today would enrage the conservative grassroots. Gingrich's personal life hardly aligns with the social conservatives in his party. His idea of health-care reform at one time included the individual mandate requiring Americans to obtain health insurance, and Gingrich once shared a love seat with Nancy Pelosi for a TV ad on the need for dialogue on climate change.

So how did Newt Gingrich end up riding the latest polling boomlet in the Republican primary? The answer is as complicated as the man and his record.

First, Gingrich has benefited from some measure of good fortune, as well as the failings of his competitors. Despite being hailed by grassroots conservatives as the rescue option for a John McCain nomination in 2007-2008, Mitt Romney has garnered little traction among the Tea Party faithful in 2011. Romney has led or run a close second in all polling this year, but he can't close the deal. Even with his money and familiarity, Romney can't get more than a quarter of primary voters to support him. That has left a wide open spot for what we have called the Not-Romney, a generic conservative candidate around which the grassroots faithful can rally.

Gingrich is not just a fighter, but a brilliant fighter. He has used the debates to put his encyclopedic knowledge on display in every aspect of policy.

Or, er ... not. Romney's competitors have had a bad record of hanging onto momentum. Herman Cain's first brief run at the lead started with a surprisingly good debate performance in May, followed by controversial statements about Muslims in government that temporarily derailed him. Michele Bachmann filled the vacuum for awhile, rising to a challenging position in national polls until Rick Perry announced his candidacy and swamped Bachmann's campaign. Bachmann ended up blowing a hole in her own campaign with her hyperbolic attacks on Perry over Gardasil vaccinations — but as it turned out, Perry didn't need any help deflating his own polling bubble. A series of disastrous debate performance transformed him from a governor with a terrific platform on the issue of the cycle — jobs — to a frequently-incoherent bumbler who couldn't remember his own attack lines.

That brings us back to Cain, who still polls high in his second boomlet despite grappling with multiple years-old allegations of sexual harassment. Conservative resentment of the media might have kept Cain's numbers up, but a recent weak debate performance on foreign policy got followed up by a mystifyingly bad interview with the Milwaukee Journal Sentinel over the weekend. Cain could not identify the Obama administration's position on Libya several months after Barack Obama authorized military force on behalf of Libyan rebels. Even worse, Cain seemed unaware that federal workers do not have collective bargaining rights, even after a national debate over public-employee unions erupted last winter — with its epicenter in Wisconsin. Voters might still defend Cain from what they see as unfair and unsubstantiated attacks on his character, but that doesn't mean they will support someone who looks unprepared for office.

One might be tempted to just dismiss the latest boomlet for Gingrich as a simple matter of waiting his turn, but it is almost certainly more than that. The previous boomlets favored candidates with one quality in common — their perceived enthusiasm for fighting Barack Obama. Tim Pawlenty never caught fire in part because of his easygoing personality, and Jon Huntsman's track record of working in the Obama administration makes him a suspect candidate, both as a fighter and on policy.

Gingrich, on the other hand, is not just a fighter, but a brilliant fighter. He has used the debates to put his encyclopedic knowledge on display in every aspect of policy. Instead of trying to scale the polling heights by fighting his fellow Republicans, Gingrich has aimed his rhetorical guns at Barack Obama and the national media, the two biggest targets for the Republican grassroots. He dressed down CBS moderator Scott Pelley in Saturday's debate on a question about killing Americans who join terrorist networks against whom Congress has already authorized military action. Those who want a fighter know that they can trust Gingrich not to embarrass them through incoherence or ignorance, and that he has a more natural inclination to confrontation than Romney.

That doesn't mean that all conservatives will cheer Gingrich's rise. The Washington Examiner gives a preview of what the rest of the field will do to Gingrich as a frontrunner, highlighting all of his heterodoxies over the years. However, unlike those who previously experienced polling bubbles, Gingrich will have little problem defending himself. And if it comes down to Gingrich and Romney, the Tea Party contingent may well put its shoulders behind a man who they know will outfight Barack Obama if a more consistently conservative alternative fails to emerge.