Newt Gingrich Destroyed by Attack Ads (December 10th - December 20th). After Herman Cain and Rick Perry self-destructed in early November, the Anti-Romney vote coalesced behind Gingrich. Gingrich then enjoyed a commanding lead over everyone else in the national and early state polls; it was the longest sustained lead held by an Anti-Romney during the primary season. Romney could have gone on the attack, but he held his fire for what seemed like an interminable period of time. Suddenly, in early-to-mid December, the Romney campaign unloaded a deluge of attack ads against Gingrich, particularly in Iowa. But would the attacks prove effective in changing Iowans' minds about Gingrich? They did. Gingrich's numbers went into a death spiral as voters learned about Gingrich's lack of conservatism and lack of electability. Gingrich placed fourth in Iowa, preventing him from winning the Iowa-South Carolina combination of which every anti-establishment candidate dreams.
Rick Santorum Runs out of Time (December 27th - January 3rd). Romney's attacks against Gingrich were timed to knock out Gingrich close enough to the Iowa Caucus so that another competitor wouldn't have enough time to rise up in his place. Before Christmas, Santorum was barely reaching double-digits, and usually didn't make the top four. After Christmas, Santorum's numbers started to climb, as Iowans considered him a more electable alternative to Perry and Gingrich. On the day of the Iowa Caucus, Santorum out-performed even his rising poll numbers. Unfortunately, he had just barely run out of time. It was reported that Romney beat Santorum by a handful of votes; they tied at 25% each. A later count showed Santorum had actually won by a handful of votes. If the contest had been held a day or two later, Santorum would have won and gotten a bounce, perhaps claiming the mantle of chief Anti-Romney. Instead, Romney was reported the winner, and Santorum wouldn't rise again until after Gingrich had been decisively defeated in Florida. By that time, Santorum had to make up a lot of ground.
Mitt Romney Beats Newt Gingrich at the Florida Debate (January 26th). After Gingrich rallied the base in debates and won the South Carolina Primary, the tide appeared to have shifted radically against Romney. A corrected tally in Iowa showed that Romney had narrowly lost there, meaning he had only won one of the first three contests. Polls in Florida showed Gingrich in the lead. Not only was Romney not going to wrap up the nomination quickly--he might even lose. But on January 26th, Romney scored a huge win against Gingrich at the final pre-Florida debate. Gingrich had claimed to be the best candidate to debate Barack Obama, but Romney obliterated Gingrich. The debate demonstrated that Gingrich actually wasn't a very good debater, and that Romney was much stronger than most voters realized. Romney went on to trounce Gingrich in the Florida Primary by 14 points, sealing his frontrunner status and taking Gingrich out of the race.
Mitt Romney Wins Michigan and Ohio (February 28th - March 6th). During the month of February 2012, the Anti-Romney vote rapidly shifted from Gingrich to Santorum. Voters are disinclined to change horses midstream, but they were desperate. Gingrich was viewed as a spent force. Santorum was the only candidate remaining who had not been vetted; voters gave him the benefit of the doubt and assumed he was a decent, electable candidate. Romney's weakness in the Midwest shone through as Santorum topped the polls in Michigan and Ohio. The Romney campaign responded by attacking Santorum's conservative credentials. Unlike the assault against Gingrich, they did not get personal and did not attack Santorum's electability. This was a mistake, and Santorum's numbers eroded only slowly, as the news media gradually did more stories about Santorum's extreme social views. It was enough--barely. Romney beat Santorum by three points in Michigan, and beat him again in Ohio by just one point. Having lost two important contests in the Midwest, Santorum could no longer hope to put together a delegate majority. After Ohio, Romney was all but guaranteed to win the nomination.