Earlier today I reported on three polls showing Mitt Romney with leads ranging from 5 to 14 points, depending on the pollster.  I missed the latest from Survey USA, a polling firm that tends to focus on metropolitan and state-wide polls, which conducted a survey over the last three days of 500 likely voters — 35% of whom have already cast an early ballot.  This poll gives Romney his biggest lead yet:

Mitt Romney is poised for a decisive win in Tuesday’s 01/31/12 Florida Presidential Primary, according to a SurveyUSA poll conducted for WFLA-TV in Tampa. The victory will give Romney 50 additional delegates, and bring his total to 69, on the march to the 1,144 delegates needed to be nominated by the Republican Party. Because Florida is one of the few “winner take all” states in 2012, the size of Romney’s victory is not as important as in a proportionally allocated state, but SurveyUSA’s final numbers show Romney 15 points atop Gingrich, 41% to 26%.

Romney is ahead in every region of the state. Gingrich draws to within single digits among Evangelicals, pro-life voters, Tea Party voters, and younger voters, but Romney overwhelms with a 25-point advantage among the affluent, a 20-point advantage among the college educated, a 20-point advantage among women, and a 19-point advantage among voters age 50+.

What about a late Gingrich surge, as Insider Advantage predicts?  Survey USA says no dice:

There is effectively no difference between those who have already voted and those who have not yet voted, so a late Gingrich surge is not anticipated.

As in the other internals, Gingrich’s low favorability (+11) seems to be his albatross.  He does better than Ron Paul, who scores an abysmal -11, but it’s only good enough for third place.  Rick Santorum actually wins in this category with a +35, but he is not as well known as Romney, who scores a +30 with higher recognition numbers.  That actually carries over among “very conservative” voters, where Gingrich gets a +25 but Romney maintains a +30, and the situation deteriorates in the other ideological categories. Among the “somewhats,” Romney gets a +32 while Gingrich only scores a +13, and among moderates — who comprise 18% of the sample overall — Romney gets a +30 to Gingrich’s -20.  The red meat carried a price in Florida, apparently.

In this poll, Romney wins the edge among evangelicals 33/28, while Santorum actually finishes below Ron Paul — an interesting result.  Romney also prevails over Gingrich among pro-life voters by seven, 35/28, which indicates that Gingrich’s attack over the last few days on Romney as “pro-abortion” didn’t find its mark.   Romney carries the very conservative vote (32% of the sample) by six, 36/30, somewhats (47% of the sample) by 18 points at 42/24, and moderates by 23 points, 44/21.  Most importantly in terms of tomorrow’s results, Romney wins the 35% of the sample who have already cast their ballots by 16 points, 47/31, and estimates of up to 600,000 early ballots cast would make that a very large lead to overcome, even if there were evidence of a late Gingrich surge.

Update: Via Nate Silver, er … yikes.  Suffolk’s last poll before the vote puts Romney up by 20 points, 47/27, with 32% having already cast their votes.  Romney prevails on immigration 35/25, the economy 50/23, and best campaign 35/15 over Gingrich.  Gingrich won for the “most negative campaign,” 37/31 over Romney.