Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) on Friday laid out his criteria for Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE's vice presidential pick, saying Republicans need someone who can forcefully make the case against Hillary Clinton Hillary Diane Rodham ClintonJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Momentum growing among Republicans for Supreme Court vote before Election Day Warning signs flash for Lindsey Graham in South Carolina MORE.

ADVERTISEMENT

Ryan, the 2012 GOP vice presidential candidate, in particular highlighted Clinton's use of a private email server while secretary of State, criticizing her for living “above the law," in a radio interview with Hugh Hewitt.

“That, to me, is one of the cardinal sins that Secretary Clinton violated,” Ryan said, according to a transcript. “And that is one of those things that the VP not only needs to point out.”

“You have to have a VP who’s ready to step up and be president at any moment, but also a vice president candidate who can articulate the policy of the forthcoming administration, and can delineate the differences,” he continued. “That’s something that the VP is going to have to do.”

Ryan said he's confident there are many capable candidates for the job.