ATLANTA >> Democrats captured control of the U.S. Senate today with a pair of historic victories in Georgia’s runoff elections, assuring slim majorities in both chambers of Congress for President-elect Joe Biden and delivering an emphatic, final rebuke to President Donald Trump in his last days in office.

The Rev. Raphael Warnock defeated Sen. Kelly Loeffler, becoming the first Black Democrat elected to the Senate from the South. And Jon Ossoff, the 33-year-old head of a video production company who has never held public office, defeated David Perdue, who recently completed his first full term as senator.

The twin victories were overshadowed in Washington when supporters of Trump stormed the Capitol. The police were forced to evacuate members of Congress as chaos and clashes erupted on the steps and rioters broke through into Capitol itself, with some entering the Senate chambers and offices in the building.

By midafternoon, protesters had gathered at Georgia’s Capitol, prompting the evacuation of Secretary of State Brad Raffensperger and some of his staff members. Raffensperger had come under fire from Trump supporters for certifying the results of Georgia’s election, delivering Georgia’s 16 electoral votes to Biden.

The results of the Georgia Senate races will reshape the balance of power in government. Although the Democrats will have the thinnest of advantages in the House and the Senate, where Vice President-elect Kamala Harris will break the 50-50 tie, they will control the committees as well as the legislation and nominations brought to the floor. That advantage will pave the way for at least some elements of Biden’s agenda.

“For the first time in six years, Democrats will operate a majority in the United States Senate — and that will be very good for the American people,” Sen. Chuck Schumer of New York, who will become the new majority leader, said at a celebratory news conference in the Capitol.

The Republicans’ losses in a state that Biden narrowly carried in November, but that still leans right, also amounted to a vivid illustration of the perils of embracing Trump. He put his diminished political capital on the line with an election-eve appearance in Northwest Georgia. And Perdue and Loeffler unwaveringly embraced the president throughout the runoff races even as he refused to acknowledge Biden’s victory and brazenly demanded that Georgia state officials overturn his loss in the state.

In the weeks leading to Tuesday’s elections, GOP officials in Georgia and Washington had worried that Republican voters would not turn out to support Perdue and Loeffler, persuaded by the president’s spurious claims of fraud that their votes would not amount to much in a compromised system.

Today, a top state election official, Gabriel Sterling, laid blame on Trump for the Republicans’ defeat, accusing the president of sparking “a civil war within a GOP that needed to be united to get through a tough fight like this.”

Sterling, a former Republican political operative who worked on President George H.W. Bush’s reelection campaign in 1992, added before Ossoff was declared the winner in his race that the president had spent more time attacking Republican officials in Georgia “than he did Raphael Warnock and, probably, Senator-to-be Ossoff.”

The criticism from Republican quarters extended to Capitol Hill. “It turns out that telling the voters that the election was rigged is not a great way to turn out your voters,” Sen. Mitt Romney of Utah said today.

The political fallout from Trump’s tenure is now clear: His single term in the White House will conclude with Republicans’ having lost the presidency, the House and the Senate on his watch.

With 98% of the vote counted late this afternoon, Warnock led Loeffler by about 62,000 votes, and Ossoff was ahead by about 25,000 votes.

No recount was expected in the Warnock-Loeffler race, Sterling said. And with thousands of votes remaining to be counted — mostly from heavily Democratic and Democratic-leaning counties around Atlanta — he said that Ossoff’s lead would also most likely grow beyond the margin of half a percentage point that would trigger a recount.

Sterling had said additional results were expected later this afternoon. But after protesters arrived and the police escorted officials to their cars, a spokesman for the secretary of state’s office said that no further updates on the vote count would be available today.

Warnock said this morning that he was honored to be elected and that he “can’t wait to get to the U.S. Senate to address the concerns of ordinary people.”

“Georgia is in such an incredible place when you think about the arc of our history,” he said in an interview on “Good Morning America.” “We are sending an African American pastor of Ebenezer Baptist Church, where Martin Luther King Jr. served, and also Jon Ossoff, a young Jewish man, the son of an immigrant, to the U.S. Senate. This is the reversal of the old Southern strategy that sought to divide people. In this moment, we’ve got to bring people together in order to do the hard work.”

Ossoff and Warnock won thanks to a frenetic get-out-the-vote push that began immediately after the November election, when no candidate in either race claimed the majority needed to avoid a runoff. Driving turnout among liberals and Black voters in the early-voting period, Democrats built an insurmountable advantage going in to election day.

They also won thanks to overwhelming margins in Georgia’s cities and decisive victories in the state’s once-Republican suburbs, and because of lackluster turnout Tuesday in the rural counties that now make up the GOP base.

The Republicans were handicapped by Trump’s refusal to acknowledge his defeat, which robbed them of what might have been their best argument for election: that they would be a check on liberal excesses in a government fully controlled by Democrats. Even before polls closed Tuesday, senior Republican campaign officials were pinning the blame on the president, saying their polling testified to the power of the “check-and-balance” argument that the party had been unable to make because of Trump.

The runoffs were also an important bellwether for a Deep South state where formerly dominant Republicans have begun to see their advantage slip because of an increasingly diverse electorate and the changing preferences of suburban voters.