Klobuchar, who’s also a Democratic presidential candidate, said she would expect the president would want to mount a defense.

“He could have his acting chief of staff, Mick Mulvaney, testify,” she told CNN’s Dana Bash. “We just found out this weekend that someone who works for Mulvaney, Michael Duffey, had sent an e-mail 90 minutes after the president made that critical call to the Ukrainian president. This guy sent an e-mail. I have it here. We just found it.“

The crux of the impeachment case has been whether Trump abused his power by seeking to deny aid to Ukraine unless it launched an investigation into the Biden family. The White House has repeatedly blocked witnesses from testifying about matters pertaining to this situation, invoking executive privilege.

The Minnesota Democrat compared the situation to when President Richard M. Nixon was facing impeachment after the 1972 Watergate break-in. (Nixon ultimately resigned in August 1974 before he could be impeached.)

“When Richard Nixon — when those hearings were held, Richard Nixon had all the president's men testify. He had major people testify from his administration,” she said.

It’s possible the Trump administration might consider Nixon’s Watergate experience to be a cautionary tale about allowing administration officials to testify. Some of the most damning testimony against Nixon came from his own administration, including White House counsel John Dean and presidential aide Alexander Butterfield, who exposed the existence of the president’s Oval Office taping system.

