Though it remains to be seen whether Republican presidential candidate Mitt Romney's selection of Rep. Paul Ryan (R-Wis.) as his running mate will produce a bounce in the polls, recent surveys — including one by Fox News, which is not known for favoring Democrats — say Romney has been losing ground against President Obama. According to Fox, Obama would get 49 percent of the vote to Romney's 40 percent if the election were held three months early, a healthy lead that is significant beyond the survey's margin of error. Just a week ago, it seems, all of the headlines suggested the race was neck-and-neck. Why has Romney fallen back in the polls? Here, four theories:

1. The Dems' Bain smears are taking a toll

Obama hasn't really pushed further ahead, says Allahpundit at Hot Air. Fox's polling sample was more heavily skewed toward the Democrats this month, which accounts for the appearance of a change from the July poll giving Obama 45 percent and Romney 41 percent. The trend lines in Romney's favorable ratings, however, "aren't encouraging after a month of Bain-mania" and calls for him to release more of his tax returns. Oddly, Obama's not yet paying much of a price for his negativity — although the survey was taken before his super PAC's "sleaze-tastic" attempt to blame Romney for the death of a steelworker's wife who lost health insurance when Bain closed her husband's mill.

2. Romney's just a terrible candidate

Conservatives can try to chalk this up to Obama's attack ads or an unfriendly media, says Joe Gandelman at The Moderate Voice. But the bottom line is that Romney "is proving to be one of the most flawed, political-talent-challenged candidates that any party has produced on the national level in several decades." His tumble in the polls isn't Team Obama's handiwork — it's Romney's own fault.

3. This is part of the normal ups and downs of a campaign

Obama indeed is enjoying his largest lead (4.4 percentage points in the average poll) of the campaign, says Nate Silver at The New York Times. "Despite all that, I think the importance of these new polls could easily be overstated — and probably will be by some in the news media." Obama's surge relative to Romney has "hardly been uniform" across the polls, and Gallup's national tracking still shows "a very flat race." More importantly, election day is still three months away, so a poll taken on Aug. 9 probably has no more bearing on the vote than one taken on July 9.

4. The numbers are simply wrong

We're in the middle of the summer doldrums, a Romney adviser tells Buzzfeed. People are paying attention to the Olympics, not the presidential race. Romney hasn't suffered from his European trip, and "there has not been any national news" that could account for such a big change. These numbers are just wrong. "Mark my words, there will be another couple of polls [soon] that potentially say something different," the adviser said last week. "We've got 88 days left, that's several lifetimes."

Read more political coverage at The Week's 2012 Election Center.