WASHINGTON (AP) — It seems like a logical pairing: Republican donors who despise Donald Trump, and two GOP presidential rivals sticking it out to keep him from the nomination.

Yet those donors have largely shunned Ted Cruz and John Kasich, depriving each of them as much as $39 million in what has become a desperate final push to topple Trump.

Yet, donors who once gave as much as allowed by law to establishment favorites Jeb Bush and Marco Rubio have mostly disappeared from the political landscape, an Associated Press analysis of campaign finance records shows.

Less than 3 percent of the nearly 14,600 donors who gave the $2,700 limit to Bush or Rubio have also ponied up the maximum amount to Kasich or Cruz, the analysis found.

Trump, who has formidably deep pockets, trounced his competitors in Tuesday's Northeast primaries, putting him in a stronger position to win the Republican nomination outright in the next six weeks of voting.

The prospect of stopping him has grown so dire that Cruz on Wednesday took the unusual step of announcing a running mate, Carly Fiorina. Earlier, he and Kasich agreed to divide their efforts in some remaining primary states to improve their chances of beating Trump.

But the big donors' continued spurning of Cruz and Kasich is one reason they haven't had more success.

"There are a significant number of major fundraisers in the Republican Party whose networks are exhausted and donors who are worn thin emotionally from the effort they made for a candidate who is no longer in the race," said Wayne Berman, a longtime Republican fundraiser. "That combination has led to many, many people sitting on the sidelines."

He's speaking from experience. Berman was the national finance chairman for Rubio and chose not to raise money for any other candidate after the Florida senator dropped out March 15.

Both Kasich and Cruz have feverishly pitched themselves to donors as the candidate best able to unify the party. It has been a particularly tough fit for Cruz, a first-term Texas senator who has made his name as an unrelenting conservative fighter — even against those in his own party.

He's had a healthy core of his own donors, including roughly 3,900 who have given the maximum amount. In fact, Cruz is the best Republican campaign fundraiser of the 2016 cycle, and started April with $8.8 million cash on hand.

Cruz has stepped up his requests of donors who might not have otherwise considered him. He and his wife, a Goldman Sachs manager on leave, talked to New York financiers last week at the Harvard Club of New York City.

The backers of former candidates are seldom responding, AP's analysis shows. Through the end of March, just 186 Bush-Rubio maxed-out donors had given the maximum to Cruz.

Fred Zeidman, a Houston-based fundraiser for Bush's failed bid, is one of them. He said he felt he "owed" the donation to Cruz because of his strong support of Israel, Zeidman's top issue.

Still, Zeidman said he can understand why lots of former Bush and Rubio donors are reluctant.

"They're keeping their powder dry until the general election, in effect just letting the primary system sort itself out," he said.

Kasich, the governor of Ohio, has attracted 174 maxed-out donors who also gave the maximum to Bush and Rubio. He's won over some of the party's top female donors, including Lynne Walton, a Wal-Mart heiress.

But Kasich has been in desperate need of more donors willing to give as much as they can. He started April with just $1.2 million on hand.

The AP analysis is based on reports of campaign contributions filed with the Federal Election Commission from the beginning of the 2016 presidential election cycle through the end of March.

The AP looked at donors who gave the maximum primary-election amount to Bush or Rubio with those who had given the maximum amount to the Democratic and Republican candidates still in the race, comparing each donor's name, city, state and ZIP code. Because the analysis excluded donors if any of the information didn't match, there could be a slight undercount.

On the Democratic side, the analysis revealed that front runner Hillary Clinton attracted about the same number of Bush-Rubio donors as did the Cruz and Kasich campaigns.

About a dozen Bush-Rubio donors have also given to Trump. A tiny core of 15 Bush-Rubio donors continued to hedge their bets by maxing out to both Cruz and Kasich. Stanley Hubbard, a billionaire Minnesota broadcast executive, has doled out checks of $2,500 or more to half a dozen presidential candidates.

Hubbard told the AP a few months ago that he wanted anyone other than Trump or Cruz at the top of the GOP ticket because he saw either of them as devastating for the party's down-ballot prospects.

Trump's continued dominance led him to revise that view: He gave Cruz a check of $2,700 on March 31.

"He's not my first choice, no," Hubbard said last week. He said he has no regrets about his heretofore fruitless campaign gifts. "Not a bit. When you give to politicians, sometimes you lose. That's the way it works."

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