Sen. Rand Paul (R-KY) warned fellow GOP senators that if four or more of them join with Democrats to entertain witness testimony, he'll make sure the Senate holds a vote on subpoenaing President Trump's preferred witnesses - including the Bidens.

"If you vote against Hunter Biden, you're voting to lose your election, basically. Seriously. That's what it is," Paul told Politico on Wednesday. "If you don't want to vote and you think you're going to have to vote against Hunter Biden, you should just vote against witnesses, period."

Paul added that if GOP senators insist on calling people "who are unhappy about being fired," referring to former National Security Adviser John Bolton, "then I think the president should get to call his [witnesses] and we should have votes on those."

"The president gets to call anybody he thinks would be good for his defense, the prosecution can call who they want, but I don't think we should selectively call witnesses that don't like the president," he said.