Sen. Pat Roberts spoke for many of his colleagues Wednesday as he lamented the grueling duty of sitting through a Senate impeachment trial.

"This is not pleasant. The circumstances are not pleasant by any means, but you just have to persevere," the Kansas Republican said. "This is tough work."

Senators had debated the trial rules until 2 a.m. the night before. "I am bushed," Roberts told the Kansas City Star.

The trial begins at 1 p.m. every day of the week except on Sunday and extends well into the night. Senators are expected, under threat of imprisonment, to sit quietly and listen.

Electronic devices, along with snacks and talking, are verboten, with the atmosphere likened to a "strong schoolhouse vibe." Roberts says he has been taking notes, and joked with reporters from the Kansas City Star that they can see where he's been dozing by the state of his handwriting.

President Trump's impeachment marks Roberts's second time as a juror.

"It was tough last time," said Roberts, 83, who voted to impeach President Bill Clinton. "We in Kansas" don't work witnesses "in the middle of the night," hide evidence "under the bed," or hedge the meaning of the word "is," Roberts said at the time. "I believe an open-minded individual applying Kansas common sense would reach the conclusion that I reached."

Roberts contrasted President Richard Nixon's 1974 Watergate trial — he was a congressional staffer at the time — which had bipartisan support with Clinton's and with Trump’s, where support falls along partisan lines.

While Senate acquittal of Trump is expected, Roberts urged colleagues to give the trial a fair chance.

"We owe this process to keep an open mind and we owe this process to fully listen to our colleagues across the aisle — unless they get too bushy-tailed," he said. "We owe the process to hear everything out and then go from there.”

Roberts, who has been in Washington since 1981, is expected to retire at the end of the year.