Feb. 4, Nevada caucuses. Mr. Romney won these by an overwhelming margin in 2008, but there was little campaigning for them because the South Carolina primary was on the same day. He should have an edge again this year because of the large number of Mormon voters in the state: 26 percent of Nevada Republican caucusgoers were Mormon in 2008, and nearly all of them voted for Mr. Romney. The financial and organizational reach of his campaign should help him in Nevada, as in other caucus states.

Still, the most recent public poll of the state, conducted by the University of Nevada Las Vegas in late December, found Mr. Romney with a relatively small advantage there, holding a 33-29 lead over Newt Gingrich. A recent internal poll for Mr. Gingrich’s campaign also showed a close race.

The Nevada polls were extremely inaccurate in 2008, projecting a much smaller margin of victory for Mr. Romney, and the same thing could happen this year.

But the 2012 and 2008 campaigns are substantially different. Although caucuses tend to benefit well-organized campaigns like Mr. Romney’s, they also tend to favor more conservative candidates whose supporters are more enthusiastic.