LAS VEGAS — After coursing through the first three intimate contests, the Republican presidential race is now accelerating to full throttle, becoming a truly national election that appears to favor celebrity front-runner Donald Trump against a bitterly divided field of opponents.

In a clear admission of Trump’s dominant standing following decisive back-to-back primary victories, his top two rivals – Sens. Ted Cruz and Marco Rubio – are not even pretending they can best the billionaire mogul on March 1, or “Super Tuesday,” when 11 states hold primaries or caucuses.

Cruz hopes to win his home state of Texas, but otherwise he and Rubio, as well as John Kasich and Ben Carson, are charting strategies to accrue convention delegates by surgically targeting slivers of the states.

The Super Tuesday contests award delegates proportionally and cover wide swaths of the country, from Massachusetts to Virginia to Alabama to Colorado. Together with the Florida, Illinois, Missouri and Ohio winner-take-all primaries March 15, they could prove determinative in the nomination battle.

Cruz is eyeing so-called Bible Belt states with disproportionately high numbers of white evangelical voters as well as caucus states where he thinks he can out-organize others. Rubio is hoping to run up his score with suburban and upwardly-mobile, mainstream voters in metropolitan areas like Atlanta, Boston, Minneapolis and Nashville.

There were signs of fresh momentum for Rubio on Sunday, as he addressed large crowds in Tennessee and Arkansas before touching down here in Las Vegas to campaign for Tuesday’s Nevada caucuses. With former Florida governor Jeb Bush’s exit from the presidential race Saturday night, Rubio is looking to quickly absorb much of the former Florida governor’s network of major donors and establishment figures, such as Sen. Dean Heller, Nev., who endorsed Rubio on Sunday.

“I will bring this party together faster than anyone else,” Rubio vowed at a crowded outdoor rally in the Nashville suburb of Franklin, Tennessee, arguing the shrinking field would play to his advantage.

But the Cruz and Rubio playbooks are borne out of limitation and underscore how difficult it will be for all of the non-Trump candidates to navigate the wake of Trump’s wins Saturday in South Carolina and 11 days earlier in New Hampshire.

Both freshman senators enter the next phase with doubts hovering over them: Is Cruz’s base of evangelicals and self-described Constitutional conservatives too narrow? Is Rubio’s demonstrated appeal across a range of demographics too shallow? And which states can either of them win?

Then there is Trump. Whether there is a ceiling to his support – and whether it would be too low for him to win a majority of Republican voters once only two candidates are left standing – remains a subject of intense debate.

That theory may not be tested as long as the Republican field remains fractured. Kasich, the Ohio governor, is vowing to soldier on into next month and sees the Michigan primary March 8 as a possible win. By doing so, he effectively deprives Rubio of the opportunity to swiftly become the establishment’s consensus alternative to Trump.

“Trump will win everything until it’s a two-person race – and he’s going to win it by a lot,” said Russ Schriefer, a veteran of past Republican presidential campaigns. “There’s a real risk that we could wake up on March 2 and Trump would have won the most number of states and have received the most number of delegates.”

That is exactly what Trump intends to do.

“It gets so big, so fast,” Trump campaign manager Corey Lewandowski said. “Our strategy is to compete everywhere. We’ll take absolutely nothing for granted.”

The race’s rhythms are amplifying, which party operatives said favors a media sensation like Trump, who can drive national headlines and will be able to hold splashy rallies in multiple states a day as he criss-crosses the country on his personal jet.

“You can’t pour coffee in a coffee shop anymore,” Republican consultant Bruce Haynes said. “You’re talking about 11 states, 30 to 40 media markets that require a significant amount of money to have any sort of presence. Walk and talk is over. It’s fly and bye.”

Having 11 contests on the same day will test the organizing abilities of the leading campaigns, including Trump’s. Until now, his team has been able to focus on one state at a time, with Lewandowski decamping to the respective state for a week to orchestrate a late ground game. But that will not be so easy anymore.

The Republican campaign moved on Sunday to Nevada, though Tuesday’s caucuses here are but a blip compared to Super Tuesday, when 595 delegates are up for grabs, awarded proportionally and in most cases by congressional district. To secure the nomination, a candidate needs 1,237 delegates.

Kasich, for instance, is unlikely to win any March 1 state outright. But he hopes to come away with delegates by targeting more moderate voters in Massachusetts, Vermont and Virginia with what his strategist, John Weaver, described as “the Kasich brand of being uplifting and inclusive.”

The Cruz and Rubio campaigns and their allied super PACs do not expect to have enough money to replicate in the Super Tuesday states the saturation level of advertising and field organizing that propelled their candidacies in Iowa, New Hampshire and South Carolina.

The pro-Rubio super PAC, Conservative Solutions PAC, announced “a multi-state, multi-million dollar advertising effort” beginning Tuesday, but officials refused to detail how much and in which TV markets.

Rubio’s campaign advisers similarly refused to discuss their Super Tuesday strategy because they did not want to reveal it to rival campaigns.

Kellyanne Conway, president of Keep the Promise I, one of the leading pro-Cruz super PACs, said her group plans to advertise in Arkansas, Georgia, Tennessee and Virginia, with Alabama and Oklahoma also in the mix. The super PAC will air positive ads about Cruz, and its negative ads will focus more on Rubio than on Trump, Conway said. That includes new spots.

“We’ve got a series on Rubio that I would call ‘chronic absenteeism’ – looking at how he’s missed votes on Planned Parenthood funding, funding for the military, about how he got himself on a 9/11 committee and didn’t attend,” Conway said.

Cruz is prioritizing caucus states with arcane rules, like Nevada – and, on March 1, Colorado and Minnesota – because he thinks his devoted network of hard-line activists and Christian conservatives will turn out in droves.

“We have our supporters identified in March 1 states and need to communicate with them,” Cruz campaign manager Jeff Roe said. “Neighbor-to-neighbor is our governing philosophy. So as it goes national, that still remains our philosophy.”

Arkansas has emerged as a key battleground. Rubio campaigned Sunday in Little Rock, and Cruz is targeting the state as well. Sarah Huckabee, who managed the presidential campaign of her father, former Arkansas governor Mike Huckabee, poured cold water on the suggestion that Cruz has the state wired.

“I live in Arkansas and I haven’t seen this mass grass-roots effort for him,” said Huckabee, who is neutral in the race. “I’m not saying he’s not more organized than others – he is – but what he has on the ground here is nothing like he had in Iowa.”

Cruz wants to rally his supporters in his home state of Texas, where two public polls in January showed him leading Trump. If he tops 50 percent, he would get all 155 delegates.

But Trump is not ceding the state. Lewandowski said Trump plans to play in traditionally Democratic congressional districts in and around San Antonio and Houston.

“I think we’re going to win Texas” Lewandowski said. “I’m going to try.”