Former Sen. John Warner (R-Va.) is encouraging Republican senators to vote in favor of calling witnesses in President Trump's impeachment trial.

Warner, 92, served in the Senate for 30 years. He said in a statement Thursday night he is "mindful of the difficult responsibilities those currently serving now shoulder. 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."

It wasn't so long ago that "senators of both major parties always worked to accommodate fellow colleagues with differing points of view to arrive at outcomes that would best serve the nation's interests," Warner said. "If witnesses are suppressed in this trial and a majority of Americans are left believing the trial was a sham, I can only imagine the lasting damage done to the Senate, and to our fragile national consensus."

He went on to "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 the impeachment trial." The senators will vote Friday on whether to allow additional witnesses, and Democrats need four Republicans to join them in order to open that door. Catherine Garcia