Guests listen to Republican presidential candidate Sen. Marco Rubio (R-Fla.) during a campaign town hall meeting Feb. 11 in Simpsonville, S.C. (Chip Somodevilla/Getty Images)
Opinion writer

South Carolina voting results may provide enough impetus for one or more candidates to get out of the race. Ben Carson has said he thought he could win South Carolina; when that delusion becomes evident on Saturday, perhaps Carson, who increasingly seems not just irrelevant but also lost, will end his campaign. And it may be that there is enough of a gap between Jeb Bush and Sen. Marco Rubio (R-Fla.) that it prompts the former to drop out. However, it is quite possible that faltering candidates will wait just a few more days to see how the Nevada caucuses, just three days later on Feb. 23, pan out.

Polling there has been scare. The latest CNN poll (with a paltry 245 GOP likely caucus-goers, so take it with a substantial grain of salt) tells us Donald Trump is far ahead (45 percent) with only two contenders above low single digits: Rubio at 19 percent and Sen. Ted Cruz (R-Tex.) at 17 percent. The results from South Carolina will obviously affect those numbers, and the extent of Trump’s organization in Nevada is uncertain.

Nevada therefore is most likely to ratify the South Carolina results. If such a huge gap remains between the top three candidates and everyone else in two consecutive races, all but the top three will have a tough time maintaining their appearances as credible candidates.

And that, it seems, is where the race will sit as the candidates head into Super Tuesday. There may be more who still hang on — Ohio Gov. John Kasich, for example, who looks ahead to Michigan (March 8) and Ohio (March 15). But a candidate who finishes in single digits in Nevada and South Carolina is unlikely to be a factor. (Most Republicans would, by then, recognize Kasich as a one-state wonder based on his second place showing in New Hampshire if he has poor results everywhere else.)

If — and let’s not forget the assumptions are dependent upon polling of questionable accuracy — that is the case, then there will be exactly one candidate, Rubio, generally acceptable to mainstream Republicans.

What could alter this scenario? Cruz, who seems to be limping in South Carolina, could underwhelm in a state in which he at one time would have been expected to win but in which he has held second place for weeks. It is bad enough that Trump is still in the race — a scenario Cruz never imagined. But it could get worse if he underperforms in South Carolina.

Part of the problem for him is the divided evangelical vote. As Politico notes:

“If everyone that was an evangelical in South Carolina, say, were members of the Family Research Council, if everyone was aware of some of the legal groups that work for Christian values, if they were all oriented that way, I think it would be a slam dunk for Cruz here,” said Oran Smith, the head of the Palmetto Family Council, an evangelical group that hosted most of the candidates at a gathering last week. “There just would not be any question, if everyone were a movement evangelical. But among more nominal or casual evangelicals, the Cruz message doesn’t resonate quite as strongly.”. . .

But tactics Cruz has been accused of using in Iowa against rival Ben Carson has sullied his candidacy in the eyes of some evangelical voters. His campaign falsely but strongly implied that Carson was exiting the race in the final hours before the Iowa Caucuses. Carson, a onetime evangelical favorite, has seen his numbers slide over the past several months, largely to Cruz’s benefit. But he is still well-liked by conservative voters—and he has not been particularly forgiving.

Those character issues are not just a problem for evangelical voters, of course.

Then there is national security, which has become a weakness for Cruz. He has tried to clean up his spotty record with rhetoric, including a hawkish speech yesterday. But many are not buying his primary conversion. McClatchy reports that “when Cruz gave an impassioned speech Tuesday in South Carolina, another military state holding a GOP primary Saturday, with a plan to build up the military, it was an expected show of good politics. Yet during his three years in the Senate, Cruz has voted against the annual defense authorization bill every time. It is always for the same reason: The bill did not prohibit the ‘indefinite detention’ of U.S. citizens arrested in the United States without trial or due process.” That position in and of itself is unpopular with many conservatives, but at any rate it seems a frivolous reason for voting against funding the entire military:

Loren Thompson, a defense expert and chief operating officer at the Lexington Institute, an Arlington, Va., think tank, said in an interview, “Cruz’s votes against the NDAA (defense authorization bill) demonstrates the dominance of an obscure domestic issue over defense. It’s a civil liberties issue, and the vote was consciously cast to appeal to the libertarian wing of the Republican Party.”

Together with his votes to curb the National Security Agency and incoherence on fighting the Islamic State, Cruz has been under fire from more hawkish candidates such as Bush and Rubio. One scenario, then, is that Cruz could stumble badly in South Carolina (as Rubio did in New Hampshire), have insufficient time to recover and then have a lackluster performance three days later in Nevada. That suggests more of a two-man race beginning with Super Tuesday.

The other scenario is a major Bush comeback. Realizing how much rides on South Carolina, Bush has been going all out. Reports suggest his ad spending is extraordinary: “Republican presidential candidates and outside support groups have already poured $24 million into political advertisements in South Carolina, the Chicago Tribune reports. . . . Almost half of that total spending – $11.6 million – has come from Right to Rise USA, the super-PAC supporting former Florida governor Jeb Bush.” Bringing his brother on the campaign trail was the sort of move one makes when you want to be certain you leave nothing on the field. If it works, and he pulls up to third or higher and then performs well in Nevada — an extraordinary comeback — that would scramble the race entirely, leaving either Cruz or Rubio at an extreme disadvantage.

In sum, South Carolina and Nevada may turn the GOP contest into a three-man race, or possibly a two-man race. If Bush can pull a surprise, he will be one of those. If not, it looks like Rubio will be a finalist along with Trump and/or Cruz — unless of course all of this is entirely wrong, which, given this race, is certainly possible.