Perhaps no Republican has had a better 2013 than Rand Paul, the Kentucky senator who drew attention and praise for his talking filibuster against the C.I.A. director nominee John Brennan, then last week won the straw poll at the Conservative Political Action Conference in Washington. Then, on Tuesday, as my colleague Ashley Parker reports, Mr. Paul gave a speech to the United States Hispanic Chamber of Commerce, outlining his plan for immigration reform.

Mr. Paul has been fairly explicit about his potential interest in running for the Republican presidential nomination in 2016, so it is safe to assume that at least some of his actions are colored by his interest in positioning himself for the primaries and caucuses. But oddsmakers continue to list Mr. Paul as something of a long shot, giving him anywhere from 12-to-1 to 28-to-1 odds against winning the nomination.

Is Mr. Paul, in fact, a viable 2016 contender? Or, like his father, Ron Paul, is he someone who might expect to win the enthusiastic support of libertarian-leaning G.O.P. voters but who might otherwise fall well short of winning a plurality or majority of the Republican electorate?

It might help to step back and consider the Republican primary electorate as a whole. The historical norm has been that Republicans are more unified in picking a candidate, while Democratic nominees must struggle to cobble together a winning plurality from among the party’s diverse constituencies. However, it is less clear that this is true today. Republicans might not have as much diversity along racial or demographic lines as Democrats do, but there are several ideological constituencies within the party that could make it hard for any candidate to win the nomination by consensus.