Donald Trump. AP Photo/Carlos Osorio Real-estate mogul Donald Trump repeatedly blasted Rep. Trey Gowdy (R-South Carolina) on Sunday after reports emerged that the influential congressman is set to endorse Sen. Marco Rubio (R-Florida) for president.

Trump, the Republican front-runner, pointed to Gowdy's high-profile October hearing on the 2012 attack in Benghazi, Libya, that left four Americans dead.

"His hearings were a disaster. Everybody was looking forward to something that was going to be really productive. And he didn't win with those hearings. It was a total not-good for Republicans and for the country," Trump said Sunday morning on "Fox & Friends."

Gowdy chairs the House Republican-led Select Committee on Benghazi, which grilled former Secretary of State Hillary Clinton on the attack for 11 hours, much of which was broadcast live on cable news. That day was widely regarded as a political win for Clinton, the Democratic front-runner, though some critics chastised that media narrative.

But Trump was clearly unhappy with how Gowdy managed that hearing.

"I mean, beyond Republicans it was very bad for the country," he said. "So I hope he does a lot better for Marco than he did for the Benghazi hearings. Because they were not good. That was not a pretty picture."

The Rubio team announced Saturday that Gowdy would campaign with the senator in Iowa and released a statement from Gowdy that praised Rubio as a "rock-solid conservative and a strong leader we can trust." Trump said he saw a flood of people on Twitter criticizing Gowdy for the move.

"I've been seeing on Twitter many, many people extremely angry about the whole thing. Because, you know, Marco's been very strong for amnesty and very weak at the border. And a lot of people are very upset with Trey Gowdy for doing that," Trump said.

Trump retweeted a number of people criticizing Gowdy, including one person who called him a "loser" and another who said he "let Hillary get away with murder."