Capitol Hill — It was, Democrats were eager to emphasize, a solemn day in the House of Representatives. Lawmakers who voted to impeach President Trump insisted the moment was not a time to celebrate.

"Today is a very sad day for all of us," Congressman Jim McGovern, chairman of the House Rules Committee, said on the House floor early in the day. The final votes came after a parade of lawmakers made their cases for and against two articles of impeachment, a marathon session that ended with the third presidential impeachment in U.S. history.

The two articles passed nearly entirely along party lines: 230-197-1 for Article I, and 229-198-1 for Article II. At the end of the vote on the second article, House Speaker Nancy Pelosi glared as someone in the chamber began to cheer, motioning for the person to knock it off. It was a moment that was emblematic of her approach to the proceedings, and of her desire to tamp down gloating by her own members.

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In the morning, Congresswoman Karen Bass told CBS News she felt "sad, and fearful" that the president would shoot off a reckless tweet in response to the impending votes. Mr. Trump obliged soon after, decrying the proceedings as an "ATTACK ON AMERICA" in an angry, exclamation-point-laden message.

The main event unfolded over more than eight hours of debate on articles alleging Mr. Trump abused his power and obstructed Congress, with time split evenly between Democrats and Republicans. A steady stream of onlookers filtered through of the viewing galleries above the House floor, watching silently as members of Congress made the same arguments they've made over and over since the impeachment inquiry began in September. Most representatives did not sit through the entirety of the day's proceedings.

After several hours of procedural maneuvering, Pelosi, clad in an understated black dress, kicked off the debate on the articles themselves shortly after noon. She said it was "tragic that the president's reckless actions make impeachment necessary."

"Today, as speaker of the House, I solemnly and sadly open the debate on the impeachment of the president of the United States," Pelosi said in her speech, which was met with a standing ovation from her fellow Democrats and stony silence from House Republicans.

A statue of President George Washington stands in the Capitol Rotunda on Wednesday, December 18, 2019. Patrick Semansky / AP

But Republicans rejected the notion that Democrats were approaching the day with anything less than glee, arguing that members of the majority had finally accomplished their long-sought goal of impeaching Mr. Trump.

"No matter what was said today and what has been said — this is not a solemn occasion," Congressman Doug Collins, the ranking member of the Judiciary Committee, said on the floor. "Why do we keep calling this a 'solemn occasion' when you've been wanting to do this ever since the president was elected?"

Republican Congressman Chris Stewart fumed against the Democrats, saying they "hate" the president and were all too happy to impeach him.

"This something you're gleeful about," Stewart accused Democrats. Another Republican, Congressman Barry Loudermilk, compared the impeachment proceedings to Jesus Christ's trial before Pontius Pilate, saying Christ was given more due process than Mr. Trump has been afforded. (Jesus, of course, was subsequently tortured and crucified.)

A sense of fatigue lingered through the Capitol, from the House floor to the press gallery above the speaker's chair, which was filled to the brim with reporters documenting the historic proceedings.

The last three months have been a marathon in the House, with dozens of witnesses testifying in closed and public hearings. The fall was marked by a deluge of revelations about Mr. Trump's request that Ukraine investigate a debunked theory about the 2016 election and a political rival, paired with the White House's staunch refusal to cooperate with the inquiry.

House Speaker Nancy Pelosi walks to the House chamber as the House of Representatives takes up articles of impeachment against President Trump on Wednesday, December 18, 2019, on Capitol Hill. Andrew Harnik / AP

Republicans greeted every development by continuing to insist the president had done nothing wrong, or at least nothing warranting impeachment. Mr. Trump himself frequently tossed his own rhetorical hand grenades into the inquiry, deriding the investigation as a "witch hunt" and criticizing career diplomats in real time as they testified before Congress.

As the House debated its way to the inexorable conclusion of impeachment on Wednesday, White House press secretary Stephanie Grisham said in a statement that the president was working all day, but "could catch some of the proceedings between meetings." He sent his furious all-caps tweet lambasting the process just minutes later.

Underlying all of the solemnity and outrage was the sense that, whatever happened in the House, impeachment will ultimately be an exercise in futility. The Republican-controlled Senate is almost certain to acquit Mr. Trump, perhaps as soon as early January.

House and Senate Democrats have railed against Senate Majority Leader Mitch McConnell for saying he would not be an "impartial juror" and for his coordination with the White House. Some in the House have argued Pelosi should withhold the articles from the Senate until McConnell agrees to fairer proceedings, although it's unclear what leverage Democrats would hope to gain by delaying a trial Republicans don't want to hold in the first place.

"We don't care whether they never come," Republican Senator John Cornyn told reporters Wednesday.

House Democrats insisted it's their constitutional duty to impeach Mr. Trump, no matter what the Senate does. All but two of the 31 Democrats who represent districts won by Mr. Trump in 2016 Republican seats in 2018 supported impeachment, putting their 2020 reelection prospects at risk, they said, because they consider it their constitutional duty.

"This decision is not, and was never about politics, and this shouldn't be about political parties or elections," said one such freshman Democrat, Congresswoman Abby Finkenauer, in a statement on Tuesday. "It's about facts, dignity in public service, and honoring those who fought and continue to fight to protect our sacred democracy."

Even as the lower chamber of Congress was debating the solemn matter of impeachment, Republicans in the upper chamber voted to confirm 13 Trump nominees to lifetime appointments on the federal bench, a stark reminder of the mutually beneficial relationship that still underpins Republicans' staunch defense of the president.