With Donald Trump gathering strength, Ted Cruz and Marco Rubio are looking to Nevada to slow his rise and push one of them forward as the alternative to the Republican front-runner.
The first-in-the-West presidential caucuses Tuesday are another contest in which the main fight appears to be the battle for second place.
So far Trump has managed to handily win New Hampshire and South Carolina even though he received only about a third of the vote in each state. That is unlikely to change unless another candidate — Rubio, Cruz or Ohio Gov. John Kasich — emerges as the sole alternative and consolidates a majority of the anti-Trump vote.
That may take some time, however, playing to Trump's continued advantage.
A win in Nevada, where he is a heavy favorite, would put the Manhattan real estate mogul and TV celebrity in a strong position heading into next week's big batch of Super Tuesday contests and make the effort to overtake the national front-runner an even steeper climb for his handful of rivals.
Cruz suffered a setback Monday after a top staffer admitted leveling an erroneous attack on Rubio.
Already fighting accusations of underhanded campaigning, Cruz asked his communications director, Rick Tyler, to resign after Tyler posted a video on social media and claimed that the senator from Florida could be heard disparaging the Bible. The allegation was false and Tyler apologized.
"This was a grave error of judgment," the senator from Texas told reporters in Las Vegas. Even if the charge had been true, he said, "we are not a campaign that is going to question the faith of another candidate."
Trump was quick to weigh in, noting that he won the evangelical vote in Saturday's South Carolina primary despite Cruz's months-long courtship and positioning as the candidate of Christian conservatives.
"The reason that Ted Cruz lost the Evangelicals in S.C. is because he is a world class LIAR, and Evangelicals do not like liars!" Trump said on Twitter.
At a rally Monday night in Las Vegas, Trump picked up the theme. "This guy is sick," he said. "There's something wrong with this guy."
Rubio, speaking to reporters before Cruz had addressed the matter, demanded an explanation.
"Who is going to be held accountable for making up this video?" Rubio said to reporters in Las Vegas before flying north to stops in Elko, Reno and Minden. "Who was held accountable for lying about Ben Carson?"
Cruz apologized to Carson during a debate this month after the Cruz campaign spread a false report that the retired neurosurgeon, who competed in Iowa for the same evangelical voters as Cruz, was quitting the race.
Last week in South Carolina, Cruz had to explain away his campaign's use of a misleading picture that had been altered to show a smiling Rubio shaking hands with President Obama.
In the latest flap, Tyler posted a video with subtitles quoting Rubio as saying there were "not many answers" in the Bible. In fact, Rubio said in the video — which was hard to understand — that the Bible has "all the answers."
Cruz was less than contrite.
At a news conference at a YMCA in Las Vegas, Cruz said Rubio's team sees a benefit to run from his record.
"They have a long record they've earned in South Carolina of engaging in this kind of trickery and impugning the integrity of whoever their opponent is to distract the attention," Cruz said.
Rubio, seeking to build on his second-place finish in South Carolina and suggest a rallying around his candidacy, announced a number of endorsements from GOP lawmakers and leaders, including Sens. Jeff Flake of Arizona and Orrin G. Hatch of Utah and Gov. Asa Hutchinson of Arkansas.
Campaigning at the Peppermill hotel-casino in Reno, Rubio largely ignored his GOP rivals and attacked the Democratic opposition.
"The winner of Nevada's Democratic caucuses is under FBI investigation," Rubio said, alluding to former Secretary of State Hillary Clinton's use of a private email server.
"Sanders is a socialist," he said of Sen. Bernie Sanders of Vermont, who calls himself a democratic socialist. "If you want to live in a socialist country, why don't you move to a socialist country?"
With less than about 48 hours to campaign before the caucuses, there was little chance for others to overtake Trump in Nevada. Kasich, looking ahead to Super Tuesday and stumping Monday in Virginia, was not even trying.
"Rubio may get some nice bounce from his South Carolina showing and some momentum from Jeb suspending his campaign," said Ryan Erwin, who was a Nevada strategist for former Florida Gov. Jeb Bush until his exit from the race Saturday night. "Cruz will pick up some rural voters concerned about federal lands and government overreach.
"But," Erwin said, "it would be an upset if Trump did not win."
Finnegan reported from Las Vegas and Lee from Reno. Times staff writer Mark Z. Barabak contributed to this report.