Senate Majority Leader Mitch McConnell (R-Ky.) leaves a news conference after speaking to reporters earlier this year. (Melina Mara/The Washington Post)

Senate Republicans unilaterally changed the rules Wednesday governing presidential nominations, a bitter escalation of the long-running dispute over the rights of the minority in a chamber once hailed for its bipartisan nature.

The move, on a pair of largely party-line votes of 51-to-48, will ease the confirmation process for President Trump’s nominees to sub-Cabinet positions in federal agencies and speed judicial nominees at the district court level.

The move exposed raw emotions delivered in highly personal terms between the two sides, particularly an angry exchange between Senate Majority Leader Mitch McConnell (R-Ky.) and Minority Leader Charles E. Schumer (D-N.Y.).

“He started this whole thing,” McConnell said just before the final vote. His face turned bright red as he glared at Schumer and accused him of putting the Senate on the road toward Wednesday’s action by convincing Democrats 18 years ago to start filibustering judges.

Moments earlier, Schumer accused the GOP leader of vowing to turn the Senate into a “conveyor belt” to approve Trump’s nominees and admonished Republicans for allowing McConnell’s “debasement of the Senate.”

Under previous Senate orders, 30 hours of debate were required for these nominees after they had cleared a procedural vote. Now, such nominees will receive two hours of formal debate before a final confirmation roll call.

In changing the rules, Republicans accused Democrats of trying to block the formation of Trump’s administration and the federal judiciary by dragging out the confirmation of noncontroversial nominees merely to create procedural gridlock.

Democrats countered that Trump, in conjunction with McConnell, has jammed the Senate with a set of historically unqualified nominees and broke with traditions of previous administrations, of both parties, in consulting with senators from the other party on many appointments.

The final steps played out in a heated debate before several parliamentary votes that were once deemed so controversial that senators call it the “nuclear option.” This violated long-standing requirements that rules changes had to be approved by a two-thirds majority.

“When history is written, this is all going to look like a tragic farce,” Sen. Michael F. Bennet (D-Colo.) said in the final minutes of debate.

Sen. Tom Cotton (R-Ark.) followed with a brief history of the nomination battles dating to the early days of the George W. Bush administration, beginning with Schumer, then a first-term senator, crafting the plan to block Bush’s judicial nominees.

“Today, Senator Schumer will reap what he sowed,” Cotton said.

Democrats have long complained about Cotton’s obstruction during Barack Obama’s second term, including his refusal to allow a vote on the nomination of Cassandra Butts, a friend of the president, to be ambassador to the Bahamas for two years. She died while waiting for Senate confirmation.

All but two Republicans supported McConnell’s rules move, with Sens. Susan Collins (R-Maine) and Mike Lee (R-Utah) opposing it.

The new rules will allow McConnell to rapidly confirm nominees to U.S. district courts, two steps below the Supreme Court, and to positions such as the assistant secretary of the Commerce Department — which was the post that triggered Wednesday’s fight and rules change.

McConnell has said shifting the federal judiciary to the right is his single biggest priority as Senate leader, beginning with his controversial decision to refuse to consider any nominee to replace Antonin Scalia on the Supreme Court after his February 2016 death.

The eventual nominee, Merrick Garland, never received a hearing in the last year of Obama’s term, keeping the seat vacant.

After Trump’s victory, Senate Republicans faced a filibuster of Neil M. Gorsuch’s nomination to fill the Scalia vacancy and executed a party-line change of rules to lower the threshold for all judicial nominees to a simple majority. Republicans cited the Democratic use of the “nuclear option” in 2013 when they lowered the filibuster hurdle for every other nominee.

The two actions, taken together, effectively left the minority party with almost no power to block presidential appointments, so long as the majority was unified in support. The last line of defense became using up every bit of time that was afforded to the minority, to try to slow the majority’s pace.

Republicans, in late 2013, began to drag out every last hour of the time allowed for Obama’s nominees, until they won the majority in the 2014 midterms and for the final two years of Obama’s administration ground the confirmation process to a virtual halt.

That left more than 100 vacancies for the lifetime appointments on federal courts at the start of Trump’s presidency. McConnell took full advantage of that opportunity and set a record pace for confirming judges to the circuit courts of appeal, the powerful benches one rung below the Supreme Court.

Democrats charged McConnell with hypocrisy as he, Trump and other Republicans boasted about the fast pace of confirming judicial nominees while complaining about obstruction by Democrats.

“My colleagues on the other side can’t have it both ways,” Sen. Ron Wyden (D-Ore.) said.

Sen. James Lankford (R-Okla.), who took a lead role in drafting the new proposal, said he has tried to get a bipartisan deal that would have changed the rules under the normal procedure, hoping that Democrats would want a potential president of their party to benefit from the faster confirmation process.

Democrats, however, were willing to vote for such a proposal only if it did not take effect until after the 2020 election, a move Republicans rejected.

“I’ve been rebuffed for two years; not a single Democrat has been willing to join us,” Lankford said.

Schumer said Republicans would regret the move.

“To do this for such blatantly political ends is simply unworthy of this institution,” he said.