Senate Republicans moved on Wednesday to resurrect unsubstantiated claims that Joseph R. Biden Jr.’s son helped a Ukrainian energy firm curry favor with the Obama administration when his father was vice president, voting over Democratic opposition to subpoena documents for an investigation that President Trump hopes to weaponize for his re-election campaign.
The party-line vote by the Homeland Security and Governmental Affairs Committee was part of an emerging push by Republicans to use their Senate majority in ways intended to help Mr. Trump as he tries to rewrite the narrative of the Russia investigation to implicate his political rivals and divert attention from the coronavirus crisis.
Even as the committee acted, Republicans on the Judiciary Committee were preparing to begin pursuing subpoenas of their own on Thursday aimed at uncovering abuses by investigators studying the 2016 Trump campaign’s ties to Russia, the first step in a series of televised hearings they have planned throughout the summer, at the president’s urging. Among those they want to call for testimony are James B. Comey, the former F.B.I. director; James R. Clapper Jr., the former director of national intelligence; Loretta E. Lynch, President Barack Obama’s attorney general; and Denis McDonough, Mr. Obama’s former chief of staff.
Republicans insist that their work is not about smearing Mr. Biden, but rather exposing potential wrongdoing and unwinding years of unfair attacks on Mr. Trump.
“If nothing happened, the American people need to know that,” Senator Ron Johnson, Republican of Wisconsin and the chairman of the Homeland Security Committee, told reporters after his meeting. “If something happened, they need to know that as well. We are just seeking the truth here.”
But the recent uptick in activity comes after Mr. Trump has prodded senators in recent weeks to “get tough” on investigations of his perceived enemies, including warning them privately in a lunch on Capitol Hill on Tuesday that if Republicans did not stick together, “vicious” Democrats would wipe them all out in November.
With their party’s political standing damaged by the pandemic, most Republicans — even those who have normally shied away from the president’s incendiary accusations — now appear ready to follow Mr. Trump’s lead.
Once reticent to echo Mr. Trump’s allegations of a “witch hunt,” Senator Mitch McConnell, Republican of Kentucky and the majority leader, has in recent days adopted the president’s lines of attack, painting him as the victim of vague and unspecified crimes by Mr. Biden and Mr. Obama. Eliding the involvement of high-level Trump appointees, Mr. McConnell suggested in remarks on the Senate floor this week that the Obama administration had used “the awesome power of the federal government to pry into their political rivals.”
“An American citizen’s campaign for the American presidency was treated like a hostile foreign power by our own law enforcement — in part because a Democrat-led executive branch manipulated documents, hid contrary evidence, and made a D.N.C.-funded dossier a launchpad for an investigation,” Mr. McConnell said on Tuesday, as he discussed the forthcoming subpoenas.
His comments came just a few days after Mr. Trump criticized the majority leader on Twitter for failing to exact revenge on Democrats, endorsing the view that Mr. McConnell would be putting the Senate Republican majority at risk if he did not take a more aggressive stance.
“Time is running out,” the president wrote. “Get tough and move quickly, or it will be too late. The Dems are vicious, but got caught. They MUST pay a big price for what they have done to our Country.”
Senate Democrats have refused to take part in the inquiries so far, dismissing them as thinly veiled political stunts.
Senator Chuck Schumer of New York, the minority leader, accused Republicans on Wednesday of turning Senate hearing rooms into de facto Fox News studios where they could “invent scapegoats for the president to use in his re-election campaign.”
In a raucous debate ahead of Wednesday’s subpoena vote, Democrats argued the Homeland Security Committee, which has broad oversight over federal response to emergencies like the pandemic, was putting more American lives at risk by neglecting its duty to hold oversight hearings with Trump administration officials.
“Today’s agenda says a lot about the Senate majority’s priorities, sadly,” said Senator Kamala Harris, Democrat of California, who is said to be under consideration as a possible running mate for Mr. Biden. “There are literally matters of life and death waiting for our committee’s attention, but instead this committee is doing the president’s personal political bidding.”
Andrew Bates, a spokesman for Mr. Biden’s campaign, said Mr. Johnson was focused on “running a political errand for Donald Trump by wasting Homeland Security Committee time and resources attempting to resurrect a craven, previously debunked smear against Vice President Biden.”
Unlike in the House, the use of subpoenas — particularly partisan ones — is exceedingly rare in the Senate.
The subpoena approved on Wednesday does not directly demand anything of the Bidens. It targets a government relations firm, Blue Star Strategies, for records about its work with Burisma, a corrupt Ukrainian energy firm that put Hunter Biden on its board.
The exact scope of Republicans’ inquiry has been unclear. Mr. Johnson has said he is interested in finding out if Burisma used the younger Mr. Biden to gain an unfair foothold in the Obama administration. Mr. Trump, on the other hand, has pushed for the Senate to investigate whether Mr. Biden as vice president tried to force Ukraine to fire a prosecutor investigating Burisma to protect his son. (Mr. Trump’s attempts to pressure Ukraine to open a similar investigation resulted in his impeachment last year.)
But during Wednesday’s debate, at least one Republican made clear he was pushing Mr. Trump’s line.
“The public deserves to know how a guy who was vice president of the United States, who is currently trying to be president, got away with using the United States government to use a foreign country to stop investigating a company that was paying his son over $80,000 a month,” said Senator Rick Scott, Republican of Florida.
The inquiry by the Senate Judiciary Committee appears to be focused on highlighting what its chairman, Senator Lindsey Graham, Republican of South Carolina, and the president have described as grave misdeeds by the investigators which they say put a cloud of suspicion around Mr. Trump beginning in 2016.
First, Mr. Graham plans to hold hearings on the government’s decision to drop charges against Michael T. Flynn, Mr. Trump’s former national security adviser who twice pleaded guilty to lying to the F.B.I., as well as on requests that Mr. Biden and other officials in the Obama administration made to reveal the identity of an unnamed American, who later turned out to be Mr. Flynn, referenced in intelligence reports about communications with Russia. Mr. Trump and his allies have insinuated that the requests were nefarious and part of a plot to entrap Mr. Flynn into lying to the authorities, but such requests are common and there is no evidence so far to back up their claim.
Mr. Graham said he would then look at mistakes made by the F.B.I. and Justice Department officials in applications to secretly wiretap a former Trump campaign adviser, Carter Page, building on a damning inspector general report that found negligence and sloppiness, but no evidence of widespread political bias. Mr. Graham ultimately intends to question whether Robert S. Mueller III, the special counsel, should have ever been appointed to carry on the Russia inquiry.
While the Judiciary Committee is scheduled to begin considering the subpoenas on Thursday, it will not vote until early June. Mr. Graham wants to be able to subpoena documents or testimony from more than 50 national security officials who worked in the White House, the Justice Department or the intelligence agencies during Mr. Obama’s presidency and the early days of Mr. Trump’s.
“I want to get all the information out there,” he told reporters on Tuesday.