By Nicholas Fandos, New York Times–

House Democrats announced on Tuesday that they would move ahead this week with two articles of impeachment charging President Trump with abuse of power and obstruction of Congress, as they accused him of violating the Constitution by pressuring Ukraine for help in the 2020 election.

Speaking from a wood-paneled reception room just off the floor of the House, Speaker Nancy Pelosi and leaders of six key committees said that Mr. Trump’s actions toward Ukraine, and his efforts to block Congress’s attempt to investigate, had left them no choice but to pursue one of the Constitution’s gravest remedies. The move will bring a sitting president to the brink of impeachment for only the fourth time in American history.

“Today, in service to our duty to the Constitution, and to our country, the House Committee on Judiciary is introducing two articles of impeachment charging the president of the United States, Donald J. Trump, with committing high crimes and misdemeanors,” said Representative Jerrold Nadler, Democrat of New York and the panel’s chairman. He stood before four American flags and a portrait of George Washington.

“Our president holds the ultimate public trust,” Mr. Nadler said. “When he betrays that trust and puts himself before country, he endangers the Constitution, he endangers our democracy, and he endangers our national security.”

The announcement comes a day after Democrats summed up the central allegations in their impeachment case against Mr. Trump: that he pressured Ukraine to announce investigations into his political rivals while withholding as leverage a coveted White House meeting for its president and $391 million in critical security assistance. His actions, they argued in a lengthy hearing at the Judiciary Committee, had placed the president’s personal political interests above those of the country, threatening the integrity of the election and national security in the process.

After more than two months of investigating the Ukraine matter, and a year of confrontation between the Democratic House and Mr. Trump, the impeachment process is now likely to unfold quickly. The Judiciary Committee plans to promptly begin debating the articles as soon as Wednesday, and could vote by Thursday to recommend them to the full House of Representatives for final approval. If the House follows through as expected next week, Mr. Trump could stand trial in the Senate early in the new year.

The Judiciary Committee planned to publicly release text of the articles later on Tuesday. While individual lawmakers will be able to propose amendments to the articles during this week’s debate and potentially force a committee vote on additional charges, they are not expected to substantively change.

Representative Adam B. Schiff of California, the chairman of the Intelligence Committee who oversaw the House’s Ukraine investigation, sought to forcefully dismiss complaints that the House was moving too quickly toward impeachment, a little more than two months after opening their inquiry.

“The argument ‘why don’t you just wait’ amounts to this: Why don’t you just let him cheat in one more election? Why not let him cheat just one more time? Why not let him have foreign help just one more time?”

The Democrats indicated that they would forgo another possible article under discussion in recent weeks that would have charged Mr. Trump with obstruction of justice based on his attempts to thwart Robert S. Mueller III’s investigation into his campaign’s ties to Russian election interference in 2016. That decision reflected a calculated move by Democrats to push forward with a narrow case against Mr. Trump based on his dealings with Ukraine, after some of their moderate lawmakers in conservative-leaning districts signaled they would not support a broader set of charges.

Though the details differ substantially, the articles of impeachment Democrats outlined on Tuesday echo those the Judiciary Committee approved in 1974 charging President Richard M. Nixon with abuse of power, obstruction of justice and contempt of Congress. Mr. Nixon resigned before the full House had a chance to vote on the articles, amid clear indications that the charges had broad support from members of both parties.

There is less overlap with the other modern presidential impeachment. In 1998, the House approved impeachment articles charging President Bill Clinton with perjury and obstruction of justice. Two other counts, of perjury and abuse of power, failed in votes on the House floor. It was that kind of split decision that Democratic leaders are determined to avoid this time around.

With all but a handful of House Republicans firmly united behind Mr. Trump, the charges Democrats have settled on are all but certain to face monolithic Republican opposition. If that does not change, and Mr. Trump continues a defiant defense, the impeachment vote against him could take place strictly along party lines, save for one independent, Representative Justin Amash of Michigan, who has signaled he will join Democrats.

The impeachment effort would also face an uphill battle in the Republican-controlled Senate, where it would take the support of two-thirds of the chamber to convict Mr. Trump and remove him from office — a highly unlikely scenario, particularly in an election year.

A little more than an hour before Democrats’ announcement, Mr. Trump declared on Twitter that it was “sheer Political Madness” to impeach a president who has done “NOTHING wrong” and overseen “perhaps the strongest economy in our country’s history.” And after it concluded, he wrote on the platform that the Democrats’ charge that he sought Ukraine’s election interference was “ridiculous” and pointed to a statement from Ukraine’s leader that he did not feel pressured to investigate the Bidens.

The White House press secretary, Stephanie Grisham, accused Democrats of “manufacturing an impeachment inquiry and forcing unfounded accusations down the throats of the American people.” Their goal, she said, was to try to use the House’s impeachment power to weaken Mr. Trump’s chances of re-election.

“The announcement of two baseless articles of impeachment does not hurt the president, it hurts the American people, who expect their elected officials to work on their behalf to strengthen our nation,” Ms. Grisham said in a statement. “The president will address these false charges in the Senate and expects to be fully exonerated, because he did nothing wrong.”

Democratic lawyers for the Judiciary Committee and the Intelligence Committee, which carried out the Ukraine inquiry, forcefully argued for the abuse of power and obstruction of Congress charges during a hearing on Monday.

Citing testimony from senior diplomats and White House officials, they accused Mr. Trump and his agents of pressuring Ukraine’s president to announce investigations of former Vice President Joseph R. Biden Jr. and an unsupported claim that Democrats conspired with Ukraine to interfere in the 2016 election. As part of the scheme, they asserted, Mr. Trump withheld a White House meeting and nearly $400 million in security assistance for the country as leverage.

They also said that Mr. Trump had systematically sought to halt their investigation by ordering government officials not to testify and refusing to hand over documents subpoenaed by the House related to the Ukraine matter.

Republicans pushed back against both conclusions, arguing that Democrats had manufactured a scandal to satiate their hunger to impeach Mr. Trump, a president whose policies they despise. They argued that the evidence gathered by the House had not proved Mr. Trump was acting to benefit himself politically when he pressed Ukraine to announce investigations into his political adversaries.

The decision to forgo a vote on an article of impeachment based on obstruction of justice was not entirely unexpected. House Democrats have debated ever since Mr. Mueller’s report became public last spring whether the behavior detailed — including 10 possible instances of obstruction — warranted such action. The issue never unified their caucus in the way the Ukraine allegations have.

Progressive lawmakers including Mr. Nadler pushed repeatedly to include an article on obstruction of justice related in the final impeachment case against Mr. Trump. But the resistance by moderates would have risked splitting the party in a vote on the House floor.