President Donald Trump used the power of the presidency to promote one of his resorts on Monday, this time pitching his struggling Doral Club in Florida as the host of next year’s G-7 summit.

Even some of Trump’s biggest supporters called him out over the obvious conflict of interest, including Rick Santorum, the former Republican senator from Pennsylvania. The two-time GOP presidential candidate said on Monday that Trump shouldn’t use his own property to host next year’s summit, calling it a “violation of the law.”

CNN’s John Berman asked Santorum, who was once in the running to be Trump’s chief of staff, what he’d say if he was in the White House and anyone, even the president, brought up the idea of hosting the event at Doral.

“Hell, no!” Santorum said.

“He doesn’t do himself any good by doing things like this,” Santorum said later in the segment. “Please, Mr. President. Stop. Please.”

Santorum chalked it up to Trump being a “promoter.”

“That’s what he does. I think that’s just who he is,” Santorum said. “It’s inappropriate. He shouldn’t do it.”

On Monday, Trump spent part of a media event with German Chancellor Angela Merkel boasting about his Florida property.

“It’s a great place. It’s got tremendous acreage. Many hundreds of acres,” Trump said. “And it’s Miami. Doral. Miami. So it’s a great area.”

He also bragged about the resort during a press conference that was later retweeted by the White House, a move critics say essentially amounted to a taxpayer-funded ad for the resort.

Walter Shaub, a former director of the Office of Government Ethics, called for an investigation into “the very real possibility that a corrupting influence tainted the procurement process” for selecting Doral.

It’s not yet clear if the summit will indeed be held at the resort.

The Washington Post reported in May that Doral was in “steep decline”; the club’s net operating income had plunged 69% over two years.

Watch the Santorum discussion below: