LAS VEGAS >> With Donald Trump’s grasp on the Republican presidential nomination tightening, the billionaire businessman’s rivals get one more chance to challenge the GOP front-runner on the debate stage before next week’s slate of Super Tuesday contests.

The situation is likely more dire for the other GOP candidates than they’d like voters to believe. Yet Sens. Marco Rubio and Ted Cruz have so far shown little willingness to take on the former reality television star when the national spotlight shines brightest.

That could change Thursday night in Houston.

“The vast and overwhelming majority of Republicans do not want Donald Trump to be our nominee,” Rubio told NBC, suggesting that Trump is winning only because the other candidates are splitting up the majority of the electorate.

For his part, the New York billionaire predicted the relative civility between Rubio and himself is about to disappear. The ninth Republican debate of the presidential campaign will take place just a few days before 11 states hold GOP elections that will either cement Trump’s dominance — or let his rivals slow his march to his party’s presidential nomination.

“Time still exists, but not much,” said Liz Mair, a Republican operative leading one of the anti-Trump movements. “The strategy of ignoring the front-runner is not working. Cruz and Rubio need to tag-team to cause Trump problems.”

How they do so is still to be determined. To date, Trump has proved largely immune to traditional political attacks, something he reveled in on Wednesday. “I seem to have a very good track record when to do go after me,” the New York real estate mogul told NBC.

The task is made more complicated by the shift from single-state campaigns to a new phase of the race, where the candidates must compete across several states at the same time. Next Tuesday features voting in a mix of states that include Texas, Georgia, Arkansas, Massachusetts and Virginia, with more to come in the weeks after.

“Now these campaigns are in the position of having to use debates to try and shape or change voter perceptions across more than a dozen states in the space of 18 or 19 days,” said Republican strategist Kevin Madden. “That’s a daunting task.”

Trump won Nevada’s presidential caucuses on Tuesday with more than 45 percent of the vote, scoring his third consecutive primary victory in dominant fashion. Rubio edged out Cruz for runner-up for the second consecutive race, with Ohio Gov. John Kasich and retired neurosurgeon Ben Carson far off the pace.

As they seek to become the Trump alternative, Cruz and Rubio have significant liabilities of their own.

Cruz comes into the debate at the weakest point of his presidential campaign after a staff shakeup and three consecutive third-place finishes.

The Texas senator ousted a senior aide on Monday after the aide promoted an inaccurate news report that Rubio had condemned the Bible during a chance encounter with Cruz’s father. The aide’s dismissal helps legitimize Trump and Rubio charges that Cruz has been running an unethical campaign.

Even while vulnerable, Cruz signaled an aggressive stance heading into the debate. He lashed out at Trump and Rubio as “Washington dealmakers” while talking to reporters in Houston on Wednesday. Rubio, Cruz said, had worked with Democrats to craft an immigration overhaul, while Trump has given money to Democrats and backed their priorities at times in recent years.

“I don’t think the people of Texas and I don’t think the people of this country want another Washington dealmaker to go and surrender more to the Democrats, giving in to the failed liberal agenda,” Cruz said.

Rubio, meanwhile, is just one debate removed from a primetime meltdown. The Florida senator repeated himself several times in a New Hampshire debate less than three weeks ago, triggering what he now calls “the New Hampshire disappointment.” He avoided a similar mistake in the subsequent debate, but critics in both parties will be laser-focused on anything that suggests the 44-year-old legislator isn’t sufficiently prepared to move into the White House.

But Rubio, who has been reluctant to publicly talk about Trump by name, stepped up his aggressiveness Wednesday.

In an appearance in Houston, he criticized Trump for what Rubio said was a failure to strongly oppose the federal health care law derided by critics as “Obamacare.”

The Florida senator also said “the front-runner in this race, Donald Trump, has said he’s not going to take sides on Israel versus the Palestinians because he wants to be an honest broker.”

Rubio said there was no such thing “because the Palestinian Authority, which has strong links to terror, they teach little kids, 5-year-olds, that it’s a glorious thing to kill Jews.” He also named Trump in accusing him of thinking “parts of Obamacare are pretty good” drawing boos.

Emboldened by the recent departure of former Florida Gov. Jeb Bush from the race, Rubio has fresh momentum after two consecutive second-place finishes. His team is convinced they must dispatch with Cruz before turning their full attention to taking down Trump.

Rubio also said that he’d respond to Trump and Cruz if attacked in Thursday’s debate, but that, “I didn’t run for office to tear up other Republicans.”

And after eight debates, it’s unclear what sort of attacks could work against Trump. As his resume would suggest, he’s proven to be a master showman on primetime television.

“It seems that the Trump people like Trump no matter what he says,” said Republican strategist John Feehery. “This debate is all about who is the Trump alternative.”

Associated Press writer Will Weissert in Houston contributed to this report.