In the cold, hard light of day following Romney's decisive win over Newt in Florida, there is no longer any credible path for Gingrich to accumulate the 1144 delegates required to win the Republican nomination. To be honest, it was always a long shot, but the odds against Newt just went up astronomically.
To begin with, the February calendar not only works in favor of Romney, but it works significantly to Newt's disadvantage. The Missouri non-binding primary on February 7 could have been an opportunity for Newt to regain momentum. Instead, he missed the filing deadline and will not be on the ballot. That leaves Rick Santorum with a clean shot to consolidate conservatives, defeat Romney, and get back in the game. The caucuses between February 4 - 11 are also no friend to Newt. Romney won all of these caucus states in 2008 by wide margins, even though McCain was judged to be the presumptive nominee. Romney has organizations in place in all four--Nevada, Minnesota, Colorado, and Maine, while Newt must now scramble to get a ground game going in these states. In addition, Ron Paul and Rick Santorum are aggressively campaigning and organizing in these states, with Paul seeing the opportunity to pull off wins in Nevada and Maine. Newt is much more likely to finish fourth in Nevada, Colorado, and Maine than he is to defeat Romney. Minnesota provides his one opportunity, but Romney has Pawlenty and the Minnesota establishment and Santorum will compete hard for the evangelical and manufacturing base there. In the Arizona and Michigan primaries, Romney has McCain in Arizona and home state advantage in Michigan. Expect Santorum to play hard in Michigan as well. February will be a long, dry spell for Newt that may break the back of his claim to be the conservative alternative to Romney while providing Santorum with the opportunity to re-emerge as the conservative choice.
Gingrich may certainly hold out to March, which on first blush provides him opportunities to resuscitate his campaign, but delegates are awarded proportionally in March, so even his wins will not produce great headway towards the nomination. Super-Tuesday presents opportunities in Georgia, Tennessee, and Oklahoma, all of which Huckabee won in 2008 while being increasing marginalized as a regional candidate. These states are off-set by Massachusetts, Vermont, which Romney will win hands down. Santorum will play in Ohio and Gingrich may not have the money to compete there and everywhere else. Gingrich is not on the ballot in Virginia, where voters will face the choice of Romney or Ron Paul. Paul could get a big boost in Virginia, if conservatives decide to make a stand there against Romney. Romney, however, will be the odds-on favorite to win Virginia. There are also three caucus states on super-Tuesday--Alaska, Idaho, and North Dakota--where Ron Paul will put on a major push and which are friendly to his message. The rest of March looks similar with states like Alabama and Mississippi that Gingrich can win, but only a proportional number of delegates.
Beginning in April, the calendar moves to winner-take-all primaries and shifts to predominantly northern states where Gingrich has virtually no hope. On April 24, Romney will win Connecticutt, Delaware, New York, and Rhode Island with a total of 159 delegates at stake. Santorum is much more likely to defeat Romney in Pennsylvania than Gingrich is, and if Gingrich competes there, he will only split the vote and give Romney a clean sweep that day. If not sooner, Gingrich will be dead as a candidate by then.
Gingrich has only one simple choice left: continue on, split the conservative vote with Santorum, and give Romney the nomination or put his ego aside, withdraw, and endorse Rick Santorum. Rick Santorum won't say that, but I just did.