Mitt Romney may not look inevitable after tonight’s South Carolina primary results — and that’s why this decision was, well, inevitable:

 Former Massachusetts governor Mitt Romney (R) said during a visit to campaign headquarters here Saturday morning that he will participate in the debate scheduled for Monday in Tampa.

His chief strategist, Stuart Stevens, told reporters Romney would also participate in Thursday’s debate in Jacksonville.

“Yeah, yeah, I’ll be doing the debate on Monday,” Romney said in response to a reporter’s question as he worked the phones calling voters at his Greenville headquarters. “Yeah, I’m in.”

Just four days ago, Romney was “wavering” on committing to more debates, in Florida or anywhere else.  Four days ago, though, he had a comfortable if not safe lead in South Carolina.  Had Newt Gingrich cratered on Thursday with the Marianne Gingrich dish, Romney may have had an opportunity to put an end to both the debates and the race.  Instead, Gingrich predictably used it to go nuclear on the media in the next debate, and lo and behold, Romney needs a way to stop Gingrich in Florida, which suddenly looks uncomfortably like Romney’s firewall rather than his coronation venue.

Speaking of which, Florida still looks pretty solid for Romney, although we haven’t seen any polling there since Gingrich caught his second wind in South Carolina, and a win for Gingrich there tonight will have some impact on the Sunshine State.  Early voting begins today in Florida, though, in sixty-two of 67 counties in the state.  Five other counties started early voting last Monday, due to a loophole in the state law, and absentee voting presumably has taken place this entire month.  Ballots cast while Romney has a 20+ point margin in polling will overwhelmingly favor him, especially since his campaign has the most organization in the state to drive that early voting.  It’s very possible that Romney could build enough of a lead in early and absentee voting, thanks to his huge early polling lead and organization, to make the Florida debates much less impactful than this week’s debates in South Carolina.

Update: Just to give an idea of the scope of the absentee ballot effort, the AP reported this on January 12th, while Romney had a solid 20+ point lead:

Voting is already well under way even though Florida doesn’t hold its GOP nominating contest until Jan. 31. And both Mitt Romney, coming off of back-to-back victories in Iowa and New Hampshire, and Ron Paul are aggressively reaching out to voters who have requested ballots.

None of their competitors has been nearly as active even though the victor in Florida would get a huge boost of momentum and all of the state’s 50 delegates to the national nominating convention.

As of Tuesday, 424,000 Republican absentee ballots had been mailed — to military personnel, overseas residents and other Floridians — and about 84,000 had been returned in a state that has 4 million registered Republican voters. Early voting in Hillsborough, Hardy, Hendry, Monroe and Collier counties begins Monday and runs through Jan. 29. Florida’s other 62 counties will hold early voting Jan. 21-28.

By this time those absentee ballots probably are well over 100,000.  In 2008, Republicans cast about 1.5 million votes in the primaries, so the absentees won’t be decisive, but they could make it a lot more difficult for late surgers like Gingrich to gain ground.

Update II: Marc Caputo reported on Thursday that the number of ballots returned has gone well beyond the 100K mark:

More than 138,000 Florida Republicans have cast mail-in absentee ballots already of the 455,622 requested so far and another 5,000 have voted early at the polls in some counties, according to Republican Party of Florida’s spokesman, Brian Hughes.

Republican insiders expect as many as a third of the GOP ballots to be cast early in the effort to choose a nominee to oppose President Barack Obama.

The total of 143,000 would be close to 10% of the votes cast in the 2008 Republican primary.  The early votes being cast starting today and the rest of the outstanding absentee ballots could mean that a third or more of the votes will already be cast before the second debate in Florida takes place.  That will give Romney a very big head start.

Update III: Caputo updated those figures this morning, and now the total is nearly 200,000:

But it could be a different story in Florida, where Republicans have been casting early votes by mail all month. Early voting at special precincts is now underway statewide as well. Only one campain, Mitt Romney’s, has made a concerted effort to target those voters.

So far, 185,435 absentee ballots have been cast and 11,836 early votes have been cast at precincts for a total of 197,271.

Assuming that Romney got 41% of these (80,881) and Gingrich 22% (43,400) as RCP’s polling average would suggest, Romney would have a 37,481 vote lead at this point in time — and that doesn’t take into account Romney’s organization and GOTV efforts on early/absentee voting.  That’s pretty significant, and as the early vote progresses, that advantage will continue to grow.  (via DebitKing)