By: Nicholas Fandos and Michael Shear of the New York Times

WASHINGTON — The House Judiciary Committee opened debate Wednesday on two articles of impeachment against President Trump, starting a somber and deeply partisan confrontation over Democrats’ charges that the president abused his power and obstructed Congress.

In a rare evening session that was only the third time in modern history the panel had met to consider removing a president, Democrats and Republicans clashed over the Constitution, the allegations against Mr. Trump and the political consequences of moving to oust him less than a year before the next election. The debate unfolded at the start of a two-day meeting that is expected to culminate on Thursday with a party-line vote to send the articles to the full House for final passage.

Leaning with equal weight on the Constitution and the findings of their two-and-a-half-month inquiry, Democrats made their case that Mr. Trump put the 2020 election and the nation’s security at risk. Not only did he use his office to pressure Ukraine to investigate his political rivals, they asserted, but he then trampled on his oath of office and the separation of powers by seeking to conceal his actions from Congress.

“The highest of high crimes is abuse of power,” said Representative Jerrold Nadler, Democrat of New York and the chairman of the committee. Describing the facts of the case against Mr. Trump as “overwhelming,” he added, “We cannot rely on an election to solve our problems when the president threatens the very integrity of that election.”

Republicans on the panel voiced their indignation about what they said was a refusal by Democrats to accept Mr. Trump’s legitimacy, portraying the bid to impeach him as little more than the climax of a three-year effort to reverse the outcome of Mr. Trump’s 2016 election victory.

They argued that the case against Mr. Trump was overstated and insufficiently proven, and they denounced the impeachment inquiry, saying it was unfair to Mr. Trump and his Republican allies.

“The big lie is that a sham impeachment is O.K., because the threat is so real and so urgent and so great,” said Representative Doug Collins of Georgia, the top Republican on the panel. Mr. Collins accused Democrats of being a “party that has lost all moorings of fairness and good taste.”

“This is as much about political expediency as anything else,” he added.

The rancorous back-and-forth stretched into the night as all 41 members on the notoriously partisan panel had the chance to deliver their opening remarks in one of the most consequential deliberations in more than two decades. The gathering unfolded exactly 21 years to the day after the Judiciary Committee voted to approve articles of impeachment against President Bill Clinton.

Mr. Nadler noted at the start that the meeting was unusual — statements are often allowed only from the chairman and the senior minority member of the committee — but said the historic nature of the proceeding warranted hearing from each member.

Seated at the wood-carved dais of the Ways and Means Committee room, the grandest meeting chamber in the House, lawmakers appeared to feel the weight of the occasion, refraining from some of the more raucous tactics that have marked the impeachment process so far in favor of passionate statements of principle.

Even as the outcome in the committee appeared clear, Mr. Nadler used his statement to appeal to Republicans to reconsider their position before it was too late.

“You still have a choice,” Mr. Nadler told the Republicans, adding, “President Trump will not be president forever.”

“When his time has passed, when his grip on our politics is gone, when our country returns — as surely it will — to calmer times and stronger leadership, history will look back on our actions here today,” he said. “How would you be remembered?”

Representative Jim Sensenbrenner, Republican of Wisconsin and one of the managers of the impeachment case against Mr. Clinton, had an appeal of his own to Democrats: “Put aside your partisan politics and don’t listen to what Pelosi, Schiff and Nadler are telling you, because the future of our country and the viability of our Constitution as the framers decided it are at stake.”

Along with the committee chairman, he was referring to Speaker Nancy Pelosi, who has kept remarkably tight control over the impeachment inquiry, and Representative Adam B. Schiff, Democrat of California and the chairman of the Intelligence Committee, who led the investigation into the president’s pressure campaign on Ukraine.

Representative Zoe Lofgren, Democrat of California, who was participating in her third impeachment inquiry, offered an explanation about this one. “It seems,” she said, “like we live in an alternate reality.”

Others warned of the political risks of the moment. Representative Ken Buck of Colorado predicted that voters would punish Democrats, particularly those whose victories in conservative districts in 2016 handed them control of the chamber.

“Say goodbye to your majority,” Mr. Buck said. “And please join us in January of 2021 when President Trump is inaugurated again.”

Democrats drew heavily on their own experiences and backgrounds as they sought to frame their views on impeachment for the history books. Some reached for the words of the founders or the annals of the law. Others quoted from scripture or spoke about loved ones. Many harked back to their unique biographies as immigrants and the legacy of painful periods in American history.

“I’m a black man representing Georgia, born when Jim Crow was alive and well,” said Representative Hank Johnson, Democrat of Georgia. “To me, the idea that elections can be undermined is not theoretical. I have constituents who remember what it is like to live in a democracy in name only.”

Representative Lucy McBath of Georgia, one of the panel’s only Democrats representing a swing district, spoke of losing her only son to gun violence — the cause that sent her to Congress. “This is not why I came to Washington,” she said, but she confirmed she would vote to impeach.

“I must vote my conscience, and I do so with a heavy heart and a grieving soul,” she said.

Mr. Nadler called a recess after the opening statements late Wednesday. He planned to reconvene the panel on Thursday to begin the protracted process of allowing members to propose edits and amendments to the two articles.

The first article accuses Mr. Trump of “ignoring and injuring national security and other vital national interests” by carrying out a scheme to corruptly solicit election assistance from Ukraine through investigations to smear his Democratic political rivals. The second article charges that the president obstructed Congress by engaging in “unprecedented, categorical and indiscriminate defiance” of House subpoenas.

No lawmaker is expected to cross party lines, and House Democratic leaders are eyeing a final vote to impeach the president for high crimes and misdemeanors as early as Tuesday.

Democrats are confident they have the votes to pass both articles even if a handful of Democrats defect.

With the outcome in the Judiciary Committee all but certain, lawmakers have begun privately appealing to the speaker to win appointments as impeachment managers when the charges are put before the Senate for trial.

In the Senate, the prospect of hosting an impeachment trial when they return from the year-end break was weighing heavily on their thinking.

Some Senate Republicans appeared to be eager for a streamlined trial without testimony by witnesses, ensuring that the spectacle of deciding on Mr. Trump’s impeachment would be over quickly so that the chamber could move on to other issues in an election year.

Senator Mitch McConnell, Republican of Kentucky and the majority leader, hinted at that preference in comments to reporters on Tuesday, saying that a majority of senators could decide after hearing arguments for both sides that “they’ve heard enough” and end the trial quickly.

On Wednesday, Mr. McConnell chastised the House for what he called “the least thorough and most unfair impeachment inquiry in modern history.”

Over lunch on Wednesday, Republican senators invited Representative Jim Jordan, Republican of Ohio, who has played a leading role in Mr. Trump’s defense in the House, and his lawyer, Stephen R. Castor, to privately offer their theory of the case for Mr. Trump’s defense.

At the White House, Mr. Trump’s legal team has been discussing the possibility of hiring Alan Dershowitz, the veteran lawyer who has defended the president, to represent him in the impeachment trial, according to a person familiar with the discussions. Mr. Dershowitz would join the president’s outside legal team, with Pat A. Cipollone, the White House counsel, taking the lead in arguing the case in the Senate.

Representative Mark Meadows, Republican of North Carolina, mentioned Mr. Dershowitz as a possibility on the House Freedom Caucus podcast, adding: “I have advocated that there needs to be one other attorney that’s added to the mix.”

The articles of impeachment, which run for nine pages, include two counts against Mr. Trump. Thursday’s session will begin with a committee clerk reading the articles aloud.

The first article, abuse of power, accused Mr. Trump of withholding $391 million in military aid and a coveted White House meeting for Ukraine’s president as leverage for extracting public announcements of investigations into former Vice President Joseph R. Biden Jr. and his son, as well as an unsubstantiated theory that Ukraine conspired with Democrats to swing the 2016 election against Mr. Trump.

The second article, obstruction of Congress, charges that Mr. Trump sought to cover up his own wrongdoing.