Donald Trump didn’t land the knockout blow he sought Tuesday, but his wins in Florida and two other states’ contests left some big Republican donors ready to throw in the towel.

Trump’s only setback of the night was in Ohio, where Governor John Kasich took first prize. (Missouri remains too close to call, according to the Associated Press.) But with no clear path to the nomination—there are fewer delegates up for grabs than he would need to clinch it—Kasich's win struck some donors as too little too late to stop Trump.

“I think he’s pretty much got the nomination locked up,” said Louis Sola, the founder of luxury yacht dealer Evermarine, who backed Jeb Bush and then Marco Rubio. While he said he thinks highly of Trump’s rival Ted Cruz, Sola said he’s unlikely to back him because he doesn’t believe Trump can be stopped. “I think we’re going to sit on the sidelines for a while,” he said.

Wealthy Republican donors looking for a more mainstream nominee have stepped up efforts in recent weeks to block Trump’s ascendancy. They flooded Florida with ads attacking the billionaire and failed to significantly dent his popularity. As a result, many donors, including Sola, are shifting their focus to Senate races where Republican candidates could be negatively affected by a Trump nomination.

Take Art Pope, a deep-pocketed donor who’s made a mark on North Carolina politics. Pope said in an interview that he’s a delegate for Rubio, who dropped out of the race after losing to Trump in his home state Tuesday, and will go to the Republican convention uncommitted.

“I’m not making a decision about who I’m supporting now,” Pope said. “Regardless of who the nominee for president is, I will very much focus my efforts on legislative races.”

Pope has a long history in North Carolina politics. He backed the Republican takeover of the state legislature and the governor's mansion, and also helped defeat Democratic Senator Kay Hagan in 2014. He said he is concerned about the impact a Trump nomination could have on the campaigns of Senator Richard Burr and North Carolina Governor Pat McCrory. Both face tough contests in November.

Pope, who’s a member of the network of conservative donors headed by Charles and David Koch, gave $250,000 to Conservative Solutions PAC, the super-PAC that backed Rubio. Pope said he had no regrets about backing the Florida senator and is now taking a wait-and-see approach.

Rubio’s super-PAC saw an infusion of cash after Bush dropped out of the race last month, narrowing the pool of establishment Republican candidates in the election. According to Federal Election Commission records, Conservative Solutions PAC had about $5.5 million in the bank as of Jan. 31. With Rubio out, that cash could provide a welcome boost to another candidate’s efforts.

Super-PACs for Cruz and Kasich say they’ll have ample resources going forward. Kristina Hernandez, a spokeswoman for Trusted Leadership PAC, an umbrella organization for the multiple super-PACs supporting Cruz, said the group had been fielding inquiries from donors throughout Wednesday.