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WASHINGTON — House Speaker Nancy Pelosi, D-Calif., said Senate Majority Leader Mitch McConnell, R-Ky., had humiliated Chief Justice John Roberts in President Donald Trump’s impeachment trial by voting against any additional witness testimony.

“It is a sad day for America to see Senator McConnell humiliate the Chief Justice of the United States into presiding over a vote which rejected our nation’s judicial norms, precedents and institutions which uphold the Constitution and the rule of law,” Pelosi wrote on Twitter on Saturday morning.

On Friday, the Senate rejected by a 51-49 vote a measure to subpoena additional witnesses in the impeachment trial. Republican Sens. Mitt Romney of Utah and Susan Collins of Maine broke from their party to vote with Democrats.

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Trump’s impeachment trial will be the first in U.S. history that does not include witness testimony as part of the proceedings.

Full coverage of President Donald Trump's impeachment trial

Democrats had argued that the Senate needed to hear from additional witnesses with firsthand knowledge of Trump's conduct toward Ukraine, including his former national security adviser John Bolton and acting White House chief of staff Mick Mulvaney.

There was some speculation early Friday morning about whether Roberts would break a deadlock in favor of the Democrats should the Senate reach a 50-50 tie on the vote to admit new testimony.

When Senate Minority Leader Chuck Schumer, D-N.Y., asked Roberts if he would intervene in the case of a tie, the chief justice said it would be "inappropriate."

"If the members of this body, elected by the people and accountable to them, divide equally on a motion, the normal rule is that the motion fails. I think it would be inappropriate for me, an unelected official from a different branch of government, to assert the power to change that result so that the motion would succeed," Roberts said.

Pelosi was not the only person to suggest Roberts had been put in an unfair position. In a statement announcing her decision Friday, Sen. Lisa Murkowski, R-Alaska, a Republican swing vote, said she did not want to "drag the Supreme Court into the fray."

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"It has also become clear some of my colleagues intend to further politicize this process, and drag the Supreme Court into the fray, while attacking the Chief Justice," Murkowski wrote. "I will not stand for nor support that effort. We have already degraded this institution for partisan political benefit, and I will not enable those who wish to pull down another.”

Final arguments in the impeachment trial are scheduled to begin next week, with Trump expected to be acquitted on both articles of impeachment Wednesday.