Republicans leaders and conservative opinion-shapers have long seriously doubted, in private and in public, Mitt Romney's chances of unseating President Obama. But now they're "coming around to a surprising new view — that Mitt Romney may well win the White House this November," says Jonathan Martin at Politico. With the economy calling in sick, Obama's attacks on Romney's business career apparently falling on deaf ears, and the race looking more and more like a virtual tie, the GOP is suddenly embracing its nominee. What changed? Here, five theories:

1. The polls are encouraging
The newest batch of polling shows the presidential race tightening, with Romney leading Obama or within the margin of error. Evidently, "the more people see and hear Mitt Romney, the more comfortable they become with him," says Rick Moran at American Thinker. Many conservatives didn't expect Romney to bounce back from his damaging primary fight so quickly, former Gov. Haley Barbour (R-Miss.) tells Politico. "That he's this close has surprised and encouraged me — and I think it has encouraged Republicans around the country."

2. Conservatives are rallying around Romney
GOP talking heads wrongly assumed that the social conservatives who trash-talked Romney in the primaries wouldn't coalesce behind him once he became "the vessel for their hopes" of defeating Obama, says American Thinker's Moran. Romney was perhaps not their first choice, but "most conservatives want to defeat Barack Obama far more than they ever wanted to beat John Kerry or Al Gore" and, if that means voting for a moderate Mormon, it seems they'll vote like hell.

3. Romney could beat Obama in the money race
In April, Romney cheered up Republicans by nearly catching up with Team Obama in fundraising. Throw in the Romney-friendly super PACs' haul, and Team Romney actually did better than the president. So much for fears that Republicans will get buried under a mountain of Obama cash —"Romney and the RNC are diminishing what advantage the Left is going to have," Barbour tells Politico.

4. Republicans have realized they'd been irrationally gloomy
Romney, like all major party nominees, always had a good shot at winning the White House, and it was crazy for GOP leaders to ever think otherwise, says Jamelle Bouie at The American Prospect. Barring a revelation "that would obviously disqualify [Mitt] in the eyes of the public (like cannibalism)," he probably has a 50-50 shot, and that was true the moment he wrapped up the GOP nod. "Republicans have been unduly paranoid about their chances," and it seems now "they've seen the error of their ways."

5. This is just spin
Of course, some of this newfound optimism is "pure spin from GOP operatives," says Richard K. Barry at The Reaction. Republican opinion-makers clearly all get the same playbook, and the most recent edition probably pointed out that "Romney is their nominee and it will do no good for them to express any doubt that he could possibly win."