One increasingly popular view of the Republican race after South Carolina is that two potential nominees remain: Donald Trump and Marco Rubio. With Jeb Bush out of the race, Ben Carson a non-factor, John Kasich looking like a regional candidate at best, and Ted Cruz coming in a disappointing third place in a state that he should have expected to win, Trump and Rubio are the only contenders left standing three states into the nomination calendar who retain the apparent capacity to amass the needed number of delegates to prevail on the first ballot at the national convention.
In some respects, this state of affairs favors Rubio. Public polling suggests that a significant share, and perhaps even a majority, of the Republican electorate is resistant to a Trump nomination, while Rubio appears to be broadly acceptable across party factions. As the other non-Trump candidates fold their campaigns or reveal themselves to be non-viable, Rubio can expect to receive a substantial boost in support. Party leaders and other conservative elites may begin to rally around Rubio in the coming weeks, attempting to persuade the Republican faithful to do likewise. Conventional wisdom has long suggested that Trump would falter once his opposition within the party united behind a single alternative candidate, and we seem to have reached the point in the race when that alternative has clearly emerged.
The main difficulty with this otherwise very plausible perspective is that it fits only imperfectly within the actual mechanics of the nomination process. First, Cruz, Kasich, and Carson all remain in the race (at least for now), and can therefore allow Trump to continue to win states without receiving an overall majority of votes even if they face diminishing odds of victory themselves. Second, Trump's back-to-back decisive victories in the otherwise sharply dissimilar states of New Hampshire and South Carolina, winning consistent levels of support across ideological and demographic categories, suggests that he cannot easily be contained geographically to a limited number of states. Third, Rubio has not yet managed to win—or even nearly win—a state himself, and it is not yet clear whether he can be considered a presumptive favorite in any of the 24 states that vote before his home state of Florida on March 15.
Unless the dynamics of the race change significantly over the next two weeks, Trump will start to build a clear lead in the national delegate count. Fortunately for Rubio, Republican Party rules allow states voting on March 15 or thereafter to apportion their delegates in a winner-take-all fashion. If he can hang in until then, Rubio can make up ground later in the race if the other candidates drop out and he starts beating Trump one-on-one in populous, winner-take-all states. But that may be what it takes to defeat the man who is now clearly the front-runner for the Republican presidential nomination.
A few other observations from the voting on Saturday:
1. Rubio received the endorsements of South Carolina's popular governor, Nikki Haley, and senator, Tim Scott, while the state's other senator Lindsey Graham backed Jeb Bush after dropping out of the presidential race himself. Endorsements probably help candidates to a degree (and Rubio might well have placed third without the support he received from Haley and Scott, given his modest margin over Cruz), but their influence, at least in this campaign, appears to be limited. (Trump, of course, is backed by no sitting Republican governor or member of Congress.)
2. The Nevada caucus is fairly trivial in terms of delegates allotted, and Hillary Clinton remained the prohibitive favorite for the Democratic nomination regardless of the outcome there on Saturday. Even so, her victory satisfied or even exceeded media expectations and therefore guaranteed her a week of positive press coverage—or, at least, a week without negative coverage—heading into the Democratic primary in South Carolina next Saturday. With little sign so far that Bernie Sanders has succeeded in making significant inroads among non-white Democrats, she is poised to win South Carolina easily and rack up a sizable delegate lead in the southern-dominated Super Tuesday vote on March 1. Sanders, for the first time, was the victim of the expectations game given his landslide victory in New Hampshire and tightening pre-caucus polls in Nevada. He remains likely to win a substantial share of delegates—who are always awarded proportionately in Democratic contests—but faces a very difficult path to the nomination.
3. The turnout rates in all three Democratic contests so far have been substantially lower than they were in 2008. While Sanders has staked the rationale for his candidacy on the emergence of a political "revolution" built on the participation of previously disaffected citizens, little evidence exists of his capacity to mobilize large numbers of these voters to support him.