Ted Cruz’s most influential backers, stunned by Donald Trump’s commanding lead and growing list of endorsements, opened a new line of attack against the GOP front-runner on Tuesday – suggesting the New Yorker is buying support.

One of Cruz’s most important surrogates in Iowa, Rep. Steve King, on Tuesday said Donald Trump has succeeded in lining up critical endorsements because he’s able to make offers that are “awfully difficult to refuse.”

“Let’s just say this: when Donald Trump decides he wants somebody on his team, he has an unlimited reservoir of resources that he can bring to bear,” King told POLITICO after Trump scored the backing of evangelical leader Jerry Falwell Jr. and anti-immigration hardliner Sheriff Joe Arpaio.

“One of them is money, but it may not be,” King said. “It might be fame, it might be the mystique of the Trump machine, it might be people are afraid of retribution and it might be people that are looking for opportunities down the line. And it might be any combination of those things and others that I haven’t said. That explains most of what you’ve seen come behind Donald Trump in one way or another.”