In the sprint to Super Tuesday, Marco Rubio is scrambling to parlay his newfound aggression against Donald Trump into enough support at the polls not to be overwhelmed by the suffocating effects of the celebrity mogul’s insurgent campaign.

The result is that, rather than aiming to triumph on the biggest day of the Republican presidential nominating calendar, the candidate seen as the party establishment’s best and perhaps only chance of defeating Trump merely hopes to hang on.

The delegate bonanza known as Super Tuesday, which features contests in 11 states and will award nearly half the number of delegates needed to claim the nomination, will test Rubio’s strategy of survival and the patience of his backers. The senator from Florida vowed here Saturday that he could lose all 15 of the first primaries and caucuses yet, because of the party’s delegate-allocation rules, still wrest the nomination from Trump at the summer convention.

“I will do whatever it takes, I will campaign as hard as it takes, I will stay in this race as long as it takes,” Rubio told a boisterous outdoor rally of 7,000 in this Atlanta suburb. “A con artist will never get control of this party.”

But some party strategists warned that if Trump sweeps the South, where many of Tuesday’s primaries are taking place, it may be too late for Rubio, Sen. Ted Cruz (Tex.) and the other candidates to stop him.

Here is what we know about who is expected to do well when 13 states head to the polls on Tuesday, March 1. (Julio Negron,Sarah Parnass/The Washington Post)

“We’re a month into this thing and Rubio still doesn’t have a W,” said Chip Saltsman, a veteran operative with experience across the South. “Any other cycle, he would be done. What if Marco Rubio would’ve won three out of the first four states? Wouldn’t everybody be saying it’s over? For some reason, Trump’s won three out of the four and they’re not saying it’s over.”

Ironically, the first key for Rubio in Tuesday’s balloting involves cheering for a Trump victory over Cruz in Texas, which would embarrass the freshman senator in his home state and block his path forward. Rubio’s other goal will be to amass delegates by finishing high enough in enough of the states to justify continuing his campaign.

“As long as you can say you’ve got a realistic chance of winning enough delegates to win the nomination, I’m not sure I subscribe to the idea that you have to win one of these states,” said Tennessee Gov. Bill Haslam, a Rubio endorser whose state votes Tuesday.

Rubio’s advisers are quick to lay out how he can mathematically prevent Trump from racking up the 1,237 delegates required to secure the nomination — and, if necessary, force a brokered convention in Cleveland.

Todd Harris, one of Rubio’s top advisers, said Saturday that he did not believe any candidate would have a majority of delegates at the start of the Republican convention in July. Asked whether Rubio would have more than Trump, he said, “I’m not prepared to say yes or no to that right now.”

Harris urged patience and predicted that the race would have “many twists and turns.”

“We are being judged based on this anachronistic sort of historical political view of how things have always been done in the past,” he said, “when everyone who is covering the race or is involved in the race knows that there is nothing about this cycle that is anything like what has happened in the past.”

Where Trump could lose, and other things to watch for on Super Tuesday

Cruz once saw Super Tuesday as the day he would take command because of the preponderance of Southern contests. But following Trump’s early momentum, his campaign envisions a scaled-back goal: victory in Texas, victories or close seconds to Trump in other states and overall second in delegates won.

Like Rubio, Cruz is hoping to change perceptions that Trump is on a fast march to the nomination. “He has a decent lead in the first two minutes of the first quarter so far,” Jeff Roe, Cruz’s campaign manager, said in an email. “The media covers it like it’s over, but it’s a long game.”

What Cruz will argue if he emerges victorious in Texas on Tuesday is that he, not Rubio, is the lone candidate who can defeat Trump.

“If Marco Rubio is out of the race, we win,” Roe said. “If we get out of the race, Donald Trump wins, because he gets a ton of our votes. It’s really as simple as that. The coalition of voters we have put together is not going to support an establishment candidate like Marco Rubio.”

The anti-Trump forces are clinging to the belief that even if Trump virtually runs the table on Tuesday, party rules will hold down his delegate haul. In Nevada, for instance, Trump won 46 percent of the vote in last Tuesday’s caucuses but only 14 of the 30 available delegates; Rubio got seven, and Cruz six.

“You have the perception of a front-runner [clashing] with the reality of a delegate count — and if you’re Rubio and Cruz, you still see a path,” longtime party strategist Carl Forti said.

That could give Rubio a chance to make up ground beginning March 15, when rules shift to award all the delegates to the winner of each state.

Rubio is banking on victories in Florida and possibly elsewhere, though when pressed by reporters here Saturday, he named only his home state.

A few well-funded super PACs are mounting a last-ditch anti-Trump assault on the airwaves. The pro-Rubio Conservative Solutions PAC is advertising in many Tuesday states, as well as Florida, Idaho, Kansas, Louisiana, Michigan and Mississippi, which have contests late next month. The group’s ad blitz in Florida is statewide and with significant volume, and the spots are almost entirely anti-Trump.

“There are two candidates with a viable path to the nomination, Marco being one of them, and we’re going to continue to focus on Donald Trump’s lack of credibility and record,” said Jeff Sadosky, the super PAC’s spokesman.

But some of the party’s biggest donors have become outright fatalistic. Fred Malek, finance chairman of the Republican Governors Association, said even “an atomic bomb” on Trump could not peel away his core supporters.

“The people who talk about stopping Trump are smoking something,” Malek said. “If a bunch of money guys came together and went after Trump, I don’t think it would have a good effect. All it would do is damage the potential nominee for our party — and it wouldn’t deprive Trump the nomination.”

Rubio is urgently trying to awaken those Republicans who are beginning to become comfortable with the possibility of Trump as their nominee. He posited Saturday that after Trump clinches the nomination, the media and Democrats would “descend on him like the hounds of hell.”

Rubio sees a couple remote possibilities for a surprise win Tuesday, including in Virginia, where he will spend all day Sunday with rallies in four cities. He also has his eye on Minnesota, which has caucuses, making the state more unpredictable.

Otherwise, Rubio is zeroing in on overperforming in suburban congressional districts such as those around Atlanta, where he will return Monday, to accrue delegates. Delegates on Tuesday will be awarded proportionally and by congressional district.

Central to Rubio’s survival is framing the contest as a mano-a-mano battle with Trump, which he tried to engineer with his feisty and relentless attacks in Thursday night’s CNN debate. To make the race truly one-on-one, however, Rubio must rely on several factors outside his direct control.

For one, Cruz is determined to deny Rubio that perch, and their chilly relationship would make an immediate alliance unlikely.

Also slowing Rubio’s efforts is the continued candidacy of Ohio Gov. John Kasich, who since his surprising second-place finish in the New Hampshire primary has attracted some current and former officeholders and establishment donors drawn to his more uplifting and moderate message.

Kasich is determined to stay in the race at least until the Ohio primary, on March 15, and his advisers argue that a win there would make Kasich the rightful establishment consensus candidate.

Then there is the neutrality of former Florida governor Jeb Bush and 2012 nominee Mitt Romney, not to mention the open hostility of New Jersey Gov. Chris Christie, who savaged Rubio on Friday in his flashy endorsement of Trump.

“The big question is, can the regular Republican forces get their act together after Trump becomes the clear delegate leader early next week?” said Mike Murphy, a longtime strategist who ran the pro-Bush super PAC Right to Rise. “Can they get Kasich out and get a well-funded stop Trump and Cruz effort on the air? Otherwise Trump will have a deadly lead by April.”

Should the battle go to the convention, former House speaker Newt Gingrich said trying to deny Trump the nomination if he is leading in the delegate count is risky.

“I don’t see a path,” Gingrich said. “This is not the time to get into some last-ditch . . . event that will get the convention to do something the American people don’t want.”

Looming on the outside is Romney, who has aggressively confronted Trump in recent days and demanded he release his tax returns, but so far has not voiced any preference for Rubio. Romney’s associates said that his endorsement is not imminent.

Republican elites long have assured themselves that Trump’s support has a high floor but also a low ceiling of about 35 percent. That thinking was turned on its head by Trump’s commanding, double-digit victory margins in New Hampshire, South Carolina and Nevada, as well as by Christie’s enthusiastic endorsement.

“Christie’s endorsement sends a signal to mainstream Republicans that, hey, this guy might be all right,” said pollster Neil Newhouse, who advised Right to Rise. “That’s a very tough combination for Marco Rubio to overcome right now.”

Robert Costa in Atlanta contributed to this report.