WASHINGTON - House Democrats unveiled two articles of impeachment against President Donald Trump on Tuesday, declaring that he "abused the powers of the Presidency" and sought to cover up his misdeeds by obstructing a congressional investigation into his dealings with Ukraine.

The introduction of two narrowly drawn articles charging Trump with abuse of power and obstruction of Congress represented the most significant step yet in Democrats' impeachment effort. Trump is just the fourth president in U.S. history to face the prospect of such a sanction for misconduct in office, which could be approved by next week on the House floor.

"It is an impeachable offense for the president to exercise the power of his public office to obtain an improper personal benefit, while ignoring or injuring the national interest," House Judiciary Committee Chairman Jerrold Nadler, D-N.Y., said Tuesday as he and other Democratic leaders announced the articles. "That is exactly what President Trump did."

Asserting that the president would "remain a threat to national security and the Constitution if allowed to remain in office," the articles accuse Trump of engaging in a corrupt scheme to solicit foreign interference to help his 2020 reelection bid.

"Using the powers of his high office, President Trump solicited the interference of a foreign government, Ukraine, in the 2020 United States Presidential election," the first article states. "He did so through a scheme or course of conduct that included soliciting the Government of Ukraine to publicly announce investigations that would benefit his reelection."

At the heart of the Democrats' case is the allegation that Trump tried to leverage a White House meeting and military aid, sought by Ukraine to combat Russian military aggression, to pressure Ukrainian President Volodymyr Zelensky to launch an investigation of former vice president Joe Biden and his son Hunter Biden, as well as a probe of an unfounded theory that Kyiv conspired with Democrats to interfere in the 2016 presidential election.

The second article alleges that Trump's "indiscriminate defiance" of Congress's impeachment probe was "offensive to, and subversive of, the Constitution."

Foreshadowing a potential party-line vote, Republicans aggressively defended Trump and accused Democratic lawmakers of abusing their power to pursue a long-sought impeachment of a president they never accepted.

"They were committed to impeachment regardless of the facts," said House Minority Whip Steve Scalise, R-La. "They're impeaching him because they're afraid he'll get reelected. ... That's the abuse of power."

Trump responded to the development Tuesday morning by attacking House Democratic leaders on Twitter and calling the impeachment process "sheer Political Madness."

At a campaign rally Tuesday night in Hershey, Pa., the president called the impeachment articles "flimsy, pathetic, ridiculous" and railed against Democrats for their inquiry. "They're impeaching me because they want to win an election, and that's the only way they can do it," he said.

But even as the political attacks flew Tuesday, the two parties also joined to advance one of Trump's top legislative priorities, announcing an agreement on the president's revised trade deal with Mexico and Canada.

The twin developments offered a stark contrast as Democrats announced the impeachment articles just minutes before declaring that they would vote on the trade deal long sought by Trump.

While some Democratic activists questioned the wisdom of handing Trump a legislative victory during the impeachment process, others said the deal would ultimately help Democrats and their constituents.

"I was elected to represent my people, not to try to deny the president from looking good," said Rep. Emanuel Cleaver, D-Mo. "And I'm 100% sure he'll mess it up. So let him look good, and then two hours later, he'll mess it up. ... He'll say something, he'll call somebody a name, he'll do something."

Trump did spend part of Tuesday hailing the U.S.-Mexico-Canada Agreement, touting it as "the best and most important trade deal ever made by the USA." But he was also consumed by the impeachment probe and an unrelated inspector general investigation of the FBI that undercut the president's claims of illegal government spying on his 2016 campaign.

"I don't know what report current Director of the FBI Christopher Wray was reading, but it sure wasn't the one given to me," the president tweeted Tuesday. "With that kind of attitude, he will never be able to fix the FBI, which is badly broken despite having some of the greatest men & women working there!"

Trump's remarkable public attack on his handpicked FBI director came one day after Justice Department Inspector General Michael Horowitz released a report rebutting conservatives' accusations that top FBI officials were driven by political bias as they investigated Trump's campaign for potential links to Russian election meddling. The report said the FBI investigation was well-founded, but it also cited broad and "serious performance failures" requiring major changes.

Wray drew Trump's ire after he told ABC News on Monday that the inspector general did not find that political bias affected the FBI's probe. He also dismissed a Trump-backed claim that Ukraine interfered in the 2016 election.

Rudy Giuliani, Trump's personal lawyer and a champion of that conspiracy theory, recently traveled to Ukraine in an attempt to collect evidence. He said Tuesday that the president asked him to brief the Justice Department and Republican senators on his findings ahead of the likely Senate impeachment trial.

"He wants me to do it," Giuliani said in a brief interview. "I'm working on pulling it together and hope to have it done by the end of the week."

It's not clear whether the Justice Department or GOP senators will want to hear from Giuliani, whose unofficial foreign policy moves in Ukraine have provided additional evidence for Democrats' impeachment effort against Trump.

Several witnesses who testified during the congressional impeachment hearings said Republicans' attempt to blame Ukraine for election meddling primarily serves the interest of Russia, which American intelligence officials say engaged in a systematic election interference campaign to help Trump in 2016.

During a joint news conference with Secretary of State Mike Pompeo on Tuesday, Russian Foreign Minister Sergei Lavrov forcefully denied that Moscow interfered and demanded that the United States provide evidence to back up the allegations. Pompeo declared that it happened and that "it's unacceptable."

Lavrov also met with Trump behind closed doors in the Oval Office on Tuesday. In a statement, the White House said that during the meeting, Trump "warned against any Russian attempts to interfere in United States elections." Speaking to reporters after the meeting, Lavrov denied that such a warning was delivered.

House Speaker Nancy Pelosi, D-Calif., said Trump's actions with Ukraine indicated that he would welcome more foreign election interference in 2020.

"If we did not hold him accountable, he would continue to undermine our election," she said Tuesday during Politico's Women Rule Summit. "If we allow one president - any president, no matter who she or he may be - to go down this path, we are saying goodbye to the republic and hello to a president king."

Congress has impeached two presidents in history: Andrew Johnson in 1868 and Bill Clinton in 1998. President Richard Nixon resigned in 1974 before the House could vote on articles of impeachment in the Watergate scandal. Lawmakers drafted three articles against Nixon, including charges of "high crimes and misdemeanors" that mirror the abuse-of-power and obstruction allegations Trump now faces.

Democrats' decision to restrict their impeachment push against Trump to two articles came after days of internal negotiations about whether to make a broad or narrow case for ousting the president. Ultimately, they decided to focus narrowly on Trump's Ukraine dealings, opting against adding charges related to special counsel Robert Mueller's probe of Russian election interference and obstruction of justice.

Democrats made only an oblique reference to Mueller's allegations, linking Trump's blockade of Congress's Ukraine investigation to his various attempts to stifle the Russia probe.

"These actions were consistent with President Trump's previous efforts to undermine United States Government investigations into foreign interference in the United States elections," the article on "obstruction of Congress" states.

Republicans blasted the obstruction charge against Trump, saying Democrats had prematurely accused him of defying Congress just two months after they began issuing subpoenas. White House press secretary Stephanie Grisham dismissed the charge as "silly," saying on Fox News that it was "code for 'he didn't play nice with us.' "

Some moderate Democrats, eager to show independence from the party, have discussed voting against the article of impeachment pertaining to obstruction of Congress. These Democrats worry that there's not enough evidence that Trump tried to flout the legislature's authority, since ultimately these matters will be decided in the courts.

While Democratic leaders appeared confident that they would be able to send the articles of impeachment to the Senate for a trial, Republican leaders in the Senate predicted that Trump would be acquitted.

Senate Majority Leader Mitch McConnell, R-Ky., signaled Tuesday that a Senate trial would start in early January and said he would be "totally surprised" if there are 67 senators who vote to remove Trump from office.

Speaking to reporters at the Capitol, McConnell said it remains unclear whether a trial would include testimony from witnesses, as Trump has publicly advocated. McConnell said he anticipates a trial in which House impeachment managers and lawyers for the president would make opening arguments.

After that, McConnell said, there would be two options: to call witnesses or to end the proceedings if a majority of the GOP-led Senate is prepared to do so.

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The Washington Post's Josh Dawsey and Kayla Epstein contributed to this report.