A few of the recent polls of South Carolina still show Mitt Romney leading but there are strong signs that Newt Gingrich has gained some serious momentum after Romney’s poor debate performance this week. For example, the Marist poll, which shows Romney with a large 10 point lead, picked up a big shift in the last day of their polling. From Marist Poll:

As the Republican presidential candidates crisscross the Palmetto State in the days leading up to Saturday’s South Carolina primary, Mitt Romney leads Newt Gingrich, 34% to 24%, among likely Republican primary voters including those who are undecided yet leaning toward a candidate based on interviews conducted on Monday and Tuesday.

Debates matter.  Romney’s Monday lead of 15 percentage points over his closest competitor, Newt Gingrich, narrowed to 5 percentage points on Tuesday following Monday night’s debate.

Even with the higher margin of error for just one day of polling, that is still a substantial one day swing.

In addition, three polls with data from yesterday came out showing Gingrich with a small lead over Romney in South Carolina. A Rasmussen poll found Gingrich 33 percent to Romney 31 percent. An InsiderAdvantage poll found Gingrich 32 percent to Romney 29 percent. Finally, PPP found Gingrich leading 34 percent to Romney’s 28 percent in its polling from yesterday.

If Gingrich wins South Carolina he has the potential to shake up the race and cause the fight to drag on. It would probably allow him to claim the title of the Romney alternative.

It is important to remember that South Carolina is an extremely favorable place for Gingrich. If he can win in South Carolina it would show he might be able to win elsewhere. If Gingrich can’t win in South Carolina, though, it is hard to picture anywhere he could win.

While it is probably a must-win for Gingrich to prove he stands a chance, it isn’t for Romney. Even if Gingrich narrowly wins there, Romney still holds a big lead in Florida and the primary schedule for February favors Romney.