(CNN) Two former Republican lawmakers urged their current successors to consider the evidence produced during the inquiry into President Donald Trump's Ukraine dealings in determining whether to support impeachment.

William Cohen, a former Republican senator from Maine and secretary of defense who backed impeachment during the Watergate inquiry, and Slade Gorton, a former Washington state Republican senator and attorney general who also backed President Richard Nixon's impeachment, made the comments on CNN's "Erin Burnett OutFront" Friday evening.

Their counsel comes on the same day that Rep. Justin Amash , a Michigan independent who left the Republican Party this summer, announced that he would support impeachment articles against Trump -- the first lawmaker to do so who is not a Democrat.

"I would say, listen to the witnesses," Cohen replied when asked what he thought of Republicans dismissing the probe as a sham. "Listen to the professionals who came before the Congress to swear under oath."

"You're saying that all those people who came before the committee are lying under oath," Cohen said, urging lawmakers "to go back and look at the entire spectrum from the Mueller report. There's a pattern here of (Trump) saying, 'I'm not beholden to anyone.' "

Read More