Republican Rep. Mark Sanford called a "hush agreement" negotiated on behalf of President Donald Trump with a porn star "deeply troubling."

Sanford became the first prominent elected Republican to publicly criticize the president on this issue and suggest that his party investigate the matter.

"If it was a Democratic president and hush money had been paid in the campaign, would there be a series of hearings going on?" he said. "I think you could probably point to a fair number of indicators that suggest there would be."

Republican Rep. Mark Sanford became the first prominent elected Republican to publicly criticize a $130,000 "hush agreement" negotiated in 2016 by President Donald Trump's lawyer with a porn star who says she had a sexual relationship with Trump in 2006.

"I think we ought to call it for what it is, which is it's deeply troubling," Sanford said on Wednesday.

Stephanie Clifford, whose stage name is Stormy Daniels, sued the president on Tuesday, claiming that the non-disclosure agreement designed to conceal the affair is invalid because the president never signed the document. According to the suit, Trump "purposely did not sign the agreement so he could later, if need be, publicly disavow any knowledge of the Hush Agreement and Ms. Clifford."

On Wednesday, White House press secretary Sarah Huckabee Sanders said the president, who denies having any relationship with Clifford, did not know about the payment.

"I believe that we need to recognize that everybody makes mistakes," Sanford said. "That having been said, what we can't do in the body politic is whitewash the past or be purely tribal in our thinking."

This comes days after the president's personal attorney initiated arbitration proceedings against Clifford in an attempt to pressure her not to speak publicly about the alleged affair.

Sanford, who had his own highly publicized extramarital affair while governor of South Carolina, cried foul on his own party, accusing it of turning a blind eye to the president's alleged actions for the purposes of political expediency.

"Let's reverse the shoes," he said. "If it was a Democratic president and hush money had been paid in the campaign, would there be a series of hearings going on? I think you could probably point to a fair number of indicators that suggest there would be."

The congressman argued that Trump's alleged affair with Clifford is "part of a larger pattern" and that the existence of a possible "hush payment" during a presidential campaign should not be ignored.

"This isn't ancient history. This is recent history," Sanford said. "And it's part of a larger pattern on this front. It's not a one-off."

Clifford has said privately that she met and had sex with Trump while attending a July 2006 celebrity golf tournament in Lake Tahoe. Trump married his third wife, Melania Trump, in 2005.

In January, In Touch Weekly, a celebrity magazine, published the transcript from a lengthy 2011 interview with Clifford in which she described details of her alleged affair with Trump, including that he nicknamed her "honey bunch" and said she was "smart and beautiful just like his daughter." The interview was conducted years before the porn star allegedly signed the non-disclosure agreement.