WASHINGTON — The “cooling saucer” of the United States Senate keeps going into the microwave.

For the third time in six years, the majority party in the Senate detonated the so-called nuclear option on Wednesday to unilaterally change years-old rules of the chamber with a simple-majority vote. This time, to work through a backlog of President Trump’s judicial and administration nominations, Republicans cut the time between ending debate and a final confirmation vote on executive-branch nominees and district court judges from 30 hours to two.

The change was a provocative step that reignited a bitter partisan fight over presidential nominations that has raged for a decade and spanned presidencies from both parties. Democrats dwelled at length over the blockade that stopped Judge Merrick B. Garland from ascending to the Supreme Court in the final year of Barack Obama’s presidency to angrily question how Republicans could complain about the handling of Mr. Trump’s nominees.

“There’s no other word but ‘hypocrisy,’” said Senator Chuck Schumer of New York, the Democratic leader.

The majority leader, Senator Mitch McConnell of Kentucky, justified his actions on the Garland nomination, saying Democrats would have done the same thing to a Republican Supreme Court nominee. And he said Democrats started the process in 2003, when they began routinely filibustering a Republican president’s nominees.