Other committees were zeroing in on similarly sensitive oversight targets. On Thursday, Democrats will begin their quest to secure the president’s long-suppressed tax returns. Representative Jerrold Nadler, Democrat of New York, warned the acting attorney general, Matthew G. Whitaker, on Wednesday that he could not avoid Democratic questioning. And a House Appropriations subcommittee chairwoman began an inquiry into administration rule-bending during the 35-day government shutdown.

WASHINGTON — The House Intelligence Committee on Wednesday launched a broad inquiry into the potential influence that Russia and other foreign powers may be exercising over President Trump, acting just hours after a defiant Speaker Nancy Pelosi declared that the House would not be cowed by the president’s “all-out threat” to drop its investigations of his administration.


“It’s our congressional responsibility, and if we didn’t do it, we would be delinquent in that,” Pelosi said of the House’s oversight role, just hours after Trump used his State of the Union address to warn that “ridiculous partisan investigations” threatened the nation’s economic health and the prospects of bipartisan legislating.

That, Pelosi said, “was a threat; it was an all-out threat.”

Despite Trump’s warning, the gears of congressional oversight — which were mostly still under Republican control during Trump’s first two years in office — began to turn in the portrait-lined hearing rooms of the House office buildings.

The Intelligence Committee held its first formal meeting of the year and promptly laid out a five-point investigation that was far broader in scope than previously expected.

Democrats will reopen the inquiry into Russia’s election interference efforts and possible collusion with the Trump campaign that the Republican majority closed last year. But they will add “interconnected lines of inquiry,” including whether Russia or other foreign actors hold financial or other leverage over Trump and his associates that at any point could have influenced US policy. Democrats also added a broadly construed obstruction of justice component to their work for the first time.


Trump dismissed the inquiry, saying he had “never heard of” the Intelligence Committee chairman, Adam B. Schiff of California, even though he has previously taunted Schiff with a vulgarism.

“He’s just a political hack. He’s trying to build a name for himself,” the president said, adding, “It’s called presidential harassment. And it’s unfortunate. And it really does hurt our country.”

Schiff shot back, “I can understand why the idea of meaningful oversight terrifies the president. Look, several associates of his have gone to jail. Others are awaiting trial. But we’re going to do our oversight. We are not going to be intimidated by his vulgar threats.”

He said the expanded Russia investigation would be done in collaboration with other committees, presumably including the Financial Services Committee, which is pursuing potential money laundering in the Trump Organization.

“Our job involves making sure the policy of the United States is being driven by the national interest, not by any financial entanglement, financial leverage, or other form of compromise,” Schiff said in a news conference.

Intelligence Committee Republicans, who have already begun to accuse the Democrats of politically motivated overreach, did not sign on to the investigation. In a separate statement, they called on Democrats to subpoena unnamed witnesses they recommended.

In its meeting, the committee also voted to share transcripts of witness interviews that it conducted related to Russian election interference with Special Counsel Robert Mueller. Mueller has already used two such transcripts to charge associates of the president with lying to Congress, and Democrats believe others could have intentionally misled the committee.


Other committees were making moves, too.

The Judiciary Committee had called a meeting Thursday to vote on a subpoena to compel testimony from Trump’s acting attorney general, if needed. Whitaker, a loyalist of the president’s who is overseeing Mueller’s work, is scheduled to testify voluntarily Friday, but Democrats have concerns that he may try to back out or dodge questions about the firing of his predecessor, the president’s attacks on the Justice Department, and other matters related to the Mueller inquiry.

“For the first two years of the Trump administration, Congress allowed government witnesses to dodge uncomfortable questions,” Nadler said in a statement. “That era is over.”

Perhaps most personally for the president, a Ways and Means oversight subcommittee will hold its first hearing Thursday to start building a public rationale to pursue Trump’s tax returns.

An obscure provision in the federal tax code gives the chairman of the committee unilateral powers to request from the Treasury Department tax information on any filer, including the president.

Democrats view obtaining Trump’s returns — which he has refused to release, defying modern political norms — as necessary for their broader inquiries into potential conflicts of interest between his role as president and his business operations, as well as accusations of money laundering that may have involved Russian oligarchs or other financial crimes, including those being pursued by the Intelligence Committee.


But the request is fraught with tension, both because of an anticipated legal challenge from the administration and pressure from the party’s left flank on leaders who are proceeding slowly to try to build an airtight public relations and legal case.

Meantime, Representative Betty McCollum of Minnesota, chairwoman of the Appropriations subcommittee that funds the Interior Department, asked the Government Accountability Office to issue a formal opinion on the administration’s diversion of user fees at the national parks to fund operations during the government shutdown. Such funds are supposed to be earmarked for long-term capital improvement projects.

“We will not be bullied by the president of the United States,” said Representative Hakeem Jeffries of New York, chairman of the House Democratic Caucus. “The days of the House operating as a wholly owned subsidiary of the Trump administration are over.”

Advisers around the president have been preparing for the congressional onslaught for months, and they know there is little hope of dissuading Democrats, who won control of the House by promising to be a check on Trump. That, and the long history of congressional oversight of the executive branch, made Trump’s comments Tuesday night all the more surprising to lawmakers.

“An economic miracle is taking place in the United States — and the only thing that can stop it are foolish wars, politics, or ridiculous partisan investigations,” the president said amid a broader call for bipartisan cooperation between the two branches. “If there is going to be peace and legislation, there cannot be war and investigation. It just doesn’t work that way!”


Pelosi said that was a false choice, telling reporters Wednesday that Democrats could engage with Trump on issues like immigration and reducing prescription drug pricing while also holding his administration accountable.

Pelosi also offered measured optimism around ongoing negotiations between appropriators from the House and Senate over a spending package to secure the southern border. But she hinted that Trump could pose a threat to any final deal.

“Left to their own devices, I think they could have an agreement by, on time by Friday,” she said. Pelosi added that she would support any such agreement, and urged the White House to “have the same attitude and respect for the appropriations process.”

Earlier, in a closed-door meeting with House Democrats, Pelosi had privately lambasted the president.

“He was a guest in our House chamber, and we treated him with more respect than he treated us,” she said, according to a Democratic aide in the room who was not authorized to discuss the private session publicly.

Pelosi also took a dig at Trump’s plan, detailed Tuesday, to invest $500 million over 10 years to developing new cures for childhood cancer, characterizing it as paltry.

“Five hundred million dollars over 10 years — are you kidding me?” she said, according to the aide. “Who gave him that figure? It’s like the cost of his protection of his Mar-a-Lago or something.”