New York (CNN) Former Congressman Joe Walsh of Illinois said Thursday that if Sen. John McCain were alive today, "he'd be slapping Lindsey Graham upside the head."

"Shame on Lindsey Graham," said Walsh, who is running for the 2020 Republican presidential nomination against President Donald Trump, of the Republican senator from South Carolina, one of Trump's strongest defenders in Congress.

"There are so many Republicans in the House and the Senate who have sold their soul to this President. Lindsey is just one of them," Walsh told CNN's Gloria Borger at the CITIZEN by CNN conference in New York.

Former South Carolina Gov. Mark Sanford, who is also running for the Republican presidential nomination, charged at the CITIZEN conference that Graham's support of the President was political.

"I think he's been transparent in saying this is in essence the cost of admission for staying relevant and therefore I'm willing to pay the price," Sanford said.

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