(CNN) He served under Presidents Ronald Reagan, George H.W. Bush, and George W. Bush, but under Donald Trump's presidency, Peter Wehner says things are different.

"I'm very uncomfortable calling myself now a Republican even though my roots are with the Republican Party," Wehner told David Axelrod on "The Axe Files," a podcast from the University of Chicago Institute of Politics and CNN.

Wehner, who now serves as a senior fellow at the Ethics and Public Policy Center , said he draws particular unease from the staunch evangelical defense of the President.

"What's happened is that a lot of these prominent evangelical Christians have gone from making a prudential judgment to being the sword and shield for Donald Trump. They are his most reliable defenders," Wehner said.

In the wake of initial reports about the President's alleged affair with porn star Stormy Daniels, conservative evangelical leader Tony Perkins said Trump gets a "mulligan" when it comes to his personal behavior.

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