Paul Gigot echoes a very tired argument about why Romney is winning:

The answer is determination, luck, and divided conservative loyalties. As to luck, the GOP’s other formidable candidates chose not to run: Jeb Bush, Paul Ryan, Mitch Daniels, Chris Christie, even Haley Barbour. Then Tim Pawlenty decided to stake his campaign on a silly Iowa straw poll and bugged out after he lost. My sources say Mr. Pawlenty regretted his decision to drop out within days, and had he stayed in he might be Mr. Romney’s main competition in Iowa today.

Gigot is actually right about Romney’s determination and the divided conservative vote, but he can’t be right about that while also claiming that Romney was “lucky” not to have to face any of these other candidates. If one or more of them had entered the race, the conservative vote would be split up among even more candidates than it is now. None of the “other formidable candidates,” not even Bush, was in a position to dominate the scene once he announced. Both Pawlenty and Perry were supposed to be “consensus” candidates opposed to Romney, but Pawlenty never won over much of a following and Perry lost most of his support within weeks of entering. It’s hard to see how a continued Pawlenty presence in the race would have made him Romney’s main competition. Pawlenty was already judged and found wanting by the people who saw more of him than anyone else in this process, so how can we still be pretending that he was a major contender? No one was still pining for Sam Brownback’s missed opportunity at this point four years ago, and Brownback and Pawlenty dropped out for the same reason: too few people were donating money to them. Writing off the straw poll wouldn’t have changed that reality. Christie might be the one politician of all those named here who posed some threat to Romney, but that is because his natural backers are the Republican moderates that make up a large part of Romney’s support. Even so, he was the last to be the focus of a presidential boomlet and would have been the latest entrant to the race if he had decided to run, so he would have been at the greatest disadvantage.

Then again, it’s not really a matter of “luck” that Ryan, Christie, Daniels and Barbour tested the waters before deciding to stay on the sidelines. Their decisions bear witness to the reality that none of them saw a chance for success. Had one or more of the conservative candidates joined the race, it would have worked to Romney’s advantage by pitting the new entrants against the rest of the field. We have seen this happen for the last two open cycles on the Republican side: a relative moderate leads the field because there are (too) many conservative challengers, and at least two or three of them have a nontrivial following. Even when a majority of the party doesn’t want the relative moderate, he can eke out victories because of the divisions among conservatives.