Romney's odds of winning the Republican nomination are currently 62%.
Romney has prevailed in spite of the deep skepticism many Republicans have about his authenticity. Romney's continued support of the healthcare plan he instituted in Massachusetts (frequently derided as "Romneycare" and compared to Obamacare) has done lasting damage to his conservative credentials. The Tea Party widely regards Romney as a "RINO." Romney, though presidential in appearance, lacks the charisma and loyal followers that normally mark a strong candidate.
How did Romney secure victory in the Republican primary? Essentially by default. Primary voters value electability above all else, and the other highly-electable candidates have either declined to run or withdrawn from the race. Chris Christie was very likely to defeat Romney, but he decided not to run. Chris Christie's decision not to run was the final domino to fall, but it was not the only one. Earlier this year, Romney faced a tough potential competitor in Mike Huckabee, who led in all of the Iowa and South Carolina polls. But Huckabee inexplicably decided not to run.
Other highly-electable consensus candidates also stepped aside. Mitch Daniels declined to enter the race, and Tim Pawlenty unwisely chose to quit the race after a poor showing in the Ames straw poll in August. This left only Romney and Jon Huntsman with a high electability ranking. If the 2012 Republican primary has proven anything, it's that the race becomes easier to win when all of your competitors forfeit.
Romney's strongest remaining competitor, Rick Perry, also self-destructed, though he has not left the race. Perry's poor debate performances and attempts to directly attack Romney on stage only served to highlight Romney's superior status.
The primary calendar isn't heavily tilted in Romney's favor, given that Iowa and South Carolina are not favorable turf. But New Hampshire has thus far been an unassailable stronghold for Romney.
National polls are again showing Romney in the lead. Yet the polls understate Romney's strength for a number of reasons. First, voters typically shift in favor of electable candidates only as voting day approaches. When that strategic shift occurs (probably in December), Romney will be the only beneficiary, since his chief competitors are considered unelectable. Second, Romney has a stronger stage presence than the last time he ran. As voting day draws closer, more voters will pay attention to the race and will see the "new" Romney. Third, Romney is better at debating than his competitors. Though Perry has a chance to improve, it's just as likely that Romney will become even more skilled at slapping him down. The more debates that take place, and the more people who watch the debates, the more Romney's image as "the adult in the room" will solidify. Fourth, not all of Romney's competitors have had their time in the sun yet; when candidates like Cain or Santorum go up in the polls, they will be subject to more scrutiny and their numbers will fall again. Finally, the Christie supporters will now move into the Romney camp. All of the money and campaign resources that have heretofore been on the sidelines will be acquired by Romney.