Then-FBI Director James B. Comey speaks to the Anti-Defamation League National Leadership Summit in Washington on May 8. (Susan Walsh/Associated Press)

House Speaker Paul Ryan (R-Wis.) said the many layers of controversy facing President Trump will not impede House Republicans from pursuing their agenda, the day after the Justice Department appointed a special counsel to investigate possible collusion between Trump associates and Russian officials.

Ryan sought to project an aura of calm while speaking with reporters Thursday as a growing sense of scandal engulfs the White House.

“It’s always nice to have less drama,” he acknowledged during a news conference. “I realize there’s a lot in the media these days. That doesn’t seize up Congress. That doesn’t stop us from doing our jobs.”

He cited tax reform, a major GOP priority, as an example, vowing it would not slip into next year.

“Drama is not helpful in getting things done,” Ryan said, “but we’re still getting things done. . . . I feel very comfortable we’ll meet this goal.”

The comments came amid a second chaotic week on Capitol Hill in the wake of Trump’s dismissal of FBI Director James B. Comey. New revelations about Trump — including his disclosure of highly classified information to Russian officials and his attempt to pressure Comey to drop an investigation of Trump’s former White House national security adviser — have left Republicans reeling and increasingly frustrated by the president’s behavior.

Asked about private chatter among some Republicans that Vice President Pence would be a better chief executive than Trump, Ryan projected disgust.

“I’m not going to give credence to that,” he said. “I’m not even going to comment on that. There’s not even a point making a comment on that.”

Attention on Capitol Hill quickly returned Thursday to Comey’s firing, as committees awaited a response to invitations for him to testify and senators prepared to receive a briefing from Deputy Attorney General Rod J. Rosenstein.

“Mr. Comey was central to the events of the past few weeks,” Senate Minority Leader Charles E. Schumer (D-N.Y.) said Thursday morning on the Senate floor. “We still need to hear from him.”

Comey has received invitations to testify from the Senate Intelligence Committee, the Senate Judiciary Committee and the House Oversight and Government Reform Committee. He has not stated publicly whether he will appear.

Meanwhile, the House Intelligence Committee announced that former CIA director John O. Brennan will testify Tuesday in both open and closed sessions about Russia’s election interference.

The appointment of Robert S. Mueller III as special counsel took the pressure off many lawmakers, who felt increasingly pressed in the past month to support an independent commission or a special prosecutor to look into the Russia matter. Still, Mueller’s appointment will not end the investigations already taking place on Capitol Hill, and lawmakers expressed a firm commitment to continuing their efforts.

The House Intelligence Committee on Thursday became the latest panel to request documents from the Justice Department about the Russia investigation and Comey’s conversations with Trump. The Senate Intelligence Committee, the Senate Judiciary Committee and the House Oversight and Government Reform Committee have already made similar requests.

“We’re going to keep doing our jobs — keep our Russia investigations going,” said Ryan, who had rejected calls for a special counsel.

Those efforts are taking place against a continually shifting backdrop of news and controversy involving the Trump White House. Earlier this week, The Washington Post revealed that Trump disclosed highly classified information to Russian officials during a meeting in the Oval Office. A day later, the New York Times reported that Trump had pressured Comey to drop an investigation of former White House national security adviser Michael T. Flynn, based on a memo Comey wrote summarizing their meeting.

The Senate Intelligence Committee issued a subpoena last week to force Flynn to turn over documents relevant to its Russia investigation. Chairman Richard Burr (R-N.C.) said Thursday that Flynn’s attorneys had not yet “indicated their intentions,” but he expressed hope that they will cooperate.

“Michael Flynn has not cooperated with the committee up to this point,” Burr told reporters on Capitol Hill. “We have not gotten the definitive answer.”

Congressional committees have sent multiple requests to the FBI and the White House to obtain any records of Trump’s conversations with Comey, as well as other Russia-related documents.

Among them was the House Oversight Committee, whose chairman appeared on television Wednesday night and disputed whether the Comey memo actually exists.

“I’m not even sure these memos exist,” Rep. Jason Chaffetz (R-Utah) said in an interview with Fox News Channel. “I’m not even sure they’re real. I just don’t know. . . . I do think it’s worthy of investigation. I think they should pursue it.”

Partisan differences also began to emerge on the matter of the special counsel.

While praising Mueller for being “as good as it gets,” Chaffetz said he ultimately disagreed with the Justice Department’s decision.

“They shouldn’t have actually appointed somebody,” he told Fox News. “They’re feeling the political heat. Maybe they’re watching a little too much television and reading too many newspapers and whatnot.”

He added that he had not seen “any evidence of actual collusion” between Trump associates and the Russian government.

“Where is the actual crime they think they need a special prosecutor to investigate?” Chaffetz said. “I haven’t seen that.”

In a separate Fox News interview, Sen. Marco Rubio (R-Fla.) cast doubt on the report that Trump had disclosed classified information to Russian officials, saying he spoke with someone who was in the meeting who had denied it.

“They vehemently and repeatedly denied that the president said or did anything that would have compromised U.S. intelligence, its sources, its methods or our intelligence relationships around the world,” Rubio said on “Fox & Friends.”

“Before we form opinions . . . we need to know what the facts are,” he said.

The Senate and House intelligence committees are the primary centers of investigation on Capitol Hill of the Russia matter, and Chaffetz has been criticized for not using his power to investigative Trump.

Rep. Elijah E. Cummings (Md.), the ranking Democrat on the oversight panel, called on Chaffetz to subpoena documents from the White House after the New York Times reported that Trump’s presidential transition team was aware of investigations of Flynn before naming him national security adviser.

“There is no longer any excuse to allow the White House to continue stonewalling,” Cummings said Thursday in a statement. “The Chairman either needs to subpoena the White House or let the Committee take a vote.”

Cummings elaborated in an interview on MSNBC’s “Morning Joe.”

“We need to look at the vetting process and how it takes place in the new administrations, whether they’re Democratic or Republican,” he said. “I’m hoping Chairman Chaffetz and I can work together to get some things done.”

Outside of the issue of Congress’s investigations, Democrats are expressing concerns about the possibility of improper influence by the Trump administration on Mueller’s investigation. Several members of the party, including House Minority Leader Nancy Pelosi (Calif.), said Mueller’s appointment must be followed by an independent commission to oversee its own Russia inquiry.

“A special prosecutor cannot take the place of a truly independent commission,” she said. “There’s reason to believe that the president was engaged in some very inappropriate activities.”

Asked if U.S. allies should be nervous about information being leaked by the president, Pelosi said the answer is obvious. “Wouldn’t you? Wouldn’t you be nervous?” she said.

Democrats’ other pressing concern is the search for Comey’s replacement.

“The next FBI director must be someone who is nonpartisan, independent, fearless and unimpeachable,” Schumer said Thursday, ruling out a politician for the role. “Anyone who suggests a lack of impartiality should not be considered.”

Senate Majority Leader Mitch McConnell (R-Ky.) did not mention any of these issues during his morning remarks on the Senate floor, focusing instead on health care.

“The entire Senate Republican conference has been at work debating ideas and making progress,” McConnell said. “I hope our friends on the other side of the aisle will join us in bringing some relief to all these families who desperately need it.”

Karoun Demirjian, Sean Sullivan and David Weigel contributed to this report.