A former Republican senator is urging members of his party to call for witnesses as part of President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE’s impeachment trial.

Former Sen. John Warner (Va.) asked Republicans to honor the nation's history of “judicial norms” as the impeachment process continues, largely echoing many Democrats that have been calling for witnesses since the start of the impeachment trial.

“As a lifelong Republican and a retired member of the U.S. Senate, who once served as a juror in a Presidential impeachment trial, I am mindful of the difficult responsibilities those currently serving now shoulder,” Warner said in a statement, shared by a New York Times reporter Thursday on Twitter.

NEW: Former Senator John Warner, a Republican and elder statesman of Virginia politics, has issued a statement calling on fellow Republicans to follow “judicial norms” by “welcoming relevant witnesses and documents” in President Trump’s impeachment trial. pic.twitter.com/GeRRjIkHfo — Sheryl Gay Stolberg (@SherylNYT) January 31, 2020

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“I believe, as I am sure you do, that not only is the President on trial, but in many ways so is the Senate itself. As such, I am strongly supportive of the efforts of my former Republican senate colleagues who are considering that the Senate accept the introduction of additional evidence that they deem relevant,” he added.

Warner said that throughout U.S. history, judicial systems have “largely supported the judicial norms of evidence, witnesses and relevant documents.”

“I respectfully urge the Senate to be guided by the rules of evidence and follow our nation’s judicial norms, precedents and institutions to uphold the constitution and the rule of law by welcoming relevant witnesses and documents as part of this impeachment trial,” he said.

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A vote on whether or not to allow witnesses will be Friday. Democrats need at least four Republicans to join them to pass the measure.

Although some GOP senators have signaled they are open to hearing from witnesses, Republicans voiced confidence Tuesday that they will be able to block witnesses.

Democrats have been pushing to hear from firsthand witnesses of Trump’s decision making with regard to Ukraine. Their push was bolstered after The New York Times reported Sunday that former national security advisor John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE claims in a manuscript of his forthcoming memoir that Trump tied Ukrainian aid to investigations into his political opponent, Joe Biden Joe BidenBiden leads Trump by 36 points nationally among Latinos: poll GOP set to release controversial Biden report Can Donald Trump maintain new momentum until this November? MORE.

Bolton has said he would testify if subpoenaed.