Ted Cruz vowed Monday that he’s “in for the distance,” but if the Texas senator loses Indiana on Tuesday he risks big donors abandoning the Stop Trump effort that has spent millions supporting him in battleground states.

More than a half-dozen Republicans involved in the pro-Cruz and anti-Trump push told POLITICO that Indiana is crucial for Cruz to keeping the cash flowing, as skittish donors have grown weary after a string of recent losses.


“If he can’t be stopped in Indiana, you will have a lot of people who just throw up their arms and say, ‘Well, I guess he can’t be stopped,’” said Erick Erickson, an influential Republican activist who has tried to organize anti-Trump forces. “I think the super donors or the megadonors — they stop spending money. They’re not going to get on board Trump, but they’re not going to continue to invest in what they perceive as a lost cause.”

After Trump rolled through the Northeast, winning every county but one in the past six states, the pressure is on Cruz — and it’s showing. Cruz has run through his entire political playbook to save Indiana.

His camp, expressing pessimism over the Texas senator's chances, is bracing for staff cuts "at a minimum" if he loses Indiana, an aide told the Associated Press on Tuesday. Cruz's campaign manager Jeff Roe, however, tweeted that the AP report is "dead wrong."

He struck a nonaggression pact with John Kasich. He bought TV ads. His supportive super PACs bought TV ads. He blitzed the Sunday shows. He barnstormed the state on a bus tour. He got the governor’s endorsement. He even named his running mate.

And if all that is not enough, it’s not clear what would be — both to anti-Trump donors and to those inside his own campaign.

“If we lose Indiana, we have to do some soul searching,” said one top Cruz adviser, adding things are looking “rough right now.”

Indeed, the most recent poll, an NBC News/Wall Street Journal survey conducted by the Marist Institute and released on Sunday, had Trump ahead of Cruz by 15 points, though previous surveys showed closer margins.

The loss could cost Cruz one of his last remaining advantages: Millions in ad support from groups like the Club for Growth, Our Principles PAC and the pro-Cruz Trusted Leadership PAC.

Those ads boosted him in Wisconsin — his most recent victory, but one that came almost a month ago — and they’re supporting Cruz’s bid in Indiana, but one operative inside a big-money Stop Trump group explained the current mindset of donors bluntly: “It’ll be tough for them to want to jump in on a major money effort in California when hopes are getting dim.”

“If Cruz loses Indiana, many donors will take a step back and reassess what may happen in California,” said Sean Noble, a Republican strategist with ties to some anti-Trump donors, including Randy Kendrick, who gave $100,000 to Our Principles PAC in March.

Fred Malek, finance chairman of the Republican Governors Association, said wealthy donors are simply “more hesitant to put large sums to work until they see more results.”

“I think donors are going to take a very hard look at that before they put in large money between Indiana and California,” Malek said.

Erickson’s ad hoc coalition of anti-Trump Republicans, for instance, is planning a conference call on Wednesday to discuss its next steps, including re-examining a third-party challenge.

“You’re already starting to see two tracks moving forward,” Erickson said, adding that a Trump win Tuesday would mean “much more energy going toward a third-party candidate.”

Indiana won’t be mathematically decisive for Trump. He can’t secure the 1,237 delegates he needs to lock up the nomination until California votes on June 7. But a victory could deliver a “psychological” blow — multiple GOP operatives used that same word — to his opposition amid accelerating talk among Republicans of coalescing behind Trump, who has already declared himself the “presumptive nominee.”

“The donors are seeing the same nightly news shows and, if that’s having a strong influence on their decisions, you have to overcome that narrative, which will be the challenge for Cruz,” said the operative working for an anti-Trump group.

In Indiana on Monday, Cruz declared, “I am in for the distance,” and over the weekend, he vowed at the California Republican Party convention, “We’re all in” in the Golden State. The Stop Trump movement has vowed to soldier on until Trump officially clinches. But 2016 has witnessed plenty of similarly resolute statements from fallen Trump foes, most notably Jeb Bush and Marco Rubio.

At one point, Rubio declared, “I don’t care if I have to get in my pickup truck and drive around the country” to battle Trump. He dropped out only weeks later.

But whether or not Cruz wants to continue on, campaign cash could be a determining factor.

The latest financial reports from Bernie Sanders offer a stark warning of what happens to campaigns when the media and public label them electoral losers. Sanders saw his monthly haul plunge by 40 percent, from $44 million in February to $25.8 million in March.

California, with its population of 38 million, is already the most expensive state to run a campaign in the country and the rules of its primary — with each of the state’s 53 congressional districts having three delegates — mean it will likely be even harder to compete on the cheap.

“Cruz’s only path would be to capture enough congressional districts in California to hold Trump under 1,237,” Noble said.

Perhaps the biggest wild card for Cruz: The financial fate of the Stop Trump super PACs rests in the hands of so few donors.

So far, much of the anti-Trump money has come from a handful of super-rich donors, including brothers Warren and Jackson T. Stephens ($7.1 million between the Club for Growth and Our Principles PAC), Richard UIhlein ($4 million), Joe and Marlene Ricketts ($5.5 million) and Paul Singer ($1.5 million).

Those four families alone could keep the anti-Trump movement afloat if they wanted. They could almost single-handedly sink it, as well, by cutting off funds.

The last week has seen a steady drumbeat toward Trump, with House Transportation Committee Chairman Bill Shuster and Veterans Affairs Committee Chairman Jeff Miller both endorsing the Manhattan businessman. Former House Speaker John Boehner and former Sen. Judd Gregg, meanwhile, both sounded off against Cruz, with Boehner calling him “Lucifer in the flesh.”

Trump seems to sense he is on the threshold of winning the nomination, saying Sunday in Indiana his opponents are “hanging by their fingertips.”

But if Cruz can pull off a surprise win, it will be his biggest comeback yet. And it would reshape the dynamic of the race entirely, making Trump’s path to 1,237 precarious — forcing him to essentially sweep California — and ensuring all of Cruz’s efforts to lock up supporters in the shadow war for delegates would matter.

Cruz himself has done little to downplay Indiana’s pivotal role. As he wrote in a fundraising email to supporters last week: “This is the single, biggest, most important day for our campaign so far.”