Mitt Romney is back in the lead for the Republican presidential nomination, according to a Fox News poll released Wednesday.

Texas Gov. Rick Perry, who had topped the polls since he entered the race in August, fell to second place. And continuing a remarkable surge from obscurity, Georgia businessman Herman Cain beat out Ron Paul for third place.

The poll showed Romney, the former governor of Massachusetts, with 23 percent support among Republican voters (unchanged from a Fox News poll last month), Perry with 19 percent (10 points down from last month) and Cain with 17 percent (triple his showing last month).

In the second tier of candidates, former House Speaker Newt Gingrich took 11 percent, Texas Rep. Ron Paul six percent and former Utah Gov. Jon Huntsman four percent. Minnesota Rep. Michele Bachmann -- once considered a top contender -- took a measly three percent, down from a 15 percent in July and eight percent in August. Former Pennsylvania Senator Rick Santorum also got three percent.

Perry became the frontrunner the moment he entered the race, and some polls in August showed him with double-digit lead over Romney. But voters have been less than thrilled with Perry's debate performances in September, and while he is by no means out of the race, the Fox News poll is an early indication that his moment might have passed.

Interestingly, when Republican voters were asked which candidate they identified most with, the results were quite different. Perry was the choice of 17 percent, Cain 14 percent, Romney 12 percent and Bachmann 10 percent.

So in terms of ideology, more Republicans identify with Perry and Cain than with Romney -- but when asked whom they would vote for, more people say Romney. This may be an indication that Republican voters are primarily concerned with nominating a person who they believe can beat President Obama, and less with nominating the person who most shares their views.

If that is the case, it doesn't bode well for Perry, Cain or Bachmann, who have run on very conservative platforms. Most primary voters may support their policy proposals -- there is no question that the Republican electorate is conservative -- but if electability is the issue, the race is Romney's to lose, because polls show him performing much better than Perry in hypothetical matchups against Obama.

Whether electability ends up being the issue depends largely on how voters view Obama's chances of being re-elected. If they think he has a good chance, they will want to nominate anyone who can beat him. But if they think, as Bachmann argued in last week's debate, that Obama's approval ratings will fall even further by the time of the election, they will want to nominate a more conservative candidate.