WASHINGTON — The indictments of three former Trump campaign officials are expected to put new pressure on the congressional panels that have been looking into the Trump campaign’s alleged ties to the Kremlin.

Democrats called Monday for redoubling the investigative efforts, as Republicans wrestled with whether to heed the president’s calls to focus their attention on Hillary Clinton instead.

Leading Democrats also said Congress should respond to Paul Manafort’s indictment by passing laws to protect special prosecutor Robert Mueller from any retaliation from President Trump.

On Monday, Trump sought to discredit Mueller’s findings, asking on Twitter why investigators were not focusing on Hillary Clinton.

Though Trump did not threaten to fire Mueller over charges filed against Manafort, Manafort’s business partner Rick Gates, and Trump campaign adviser George Papadopoulos, Democrats warned Monday that protecting Mueller would be of the utmost importance.

‘‘It is imperative that Congress take action now to protect the independence of the special counsel, wherever or however high his investigation may lead,’’ said Senator Mark R. Warner, a Virginia Democrat who is the vice chairman of the Senate Intelligence Committee, in a statement.

Warner added that Congress ‘‘must also make it clear’’ that any attempts to pardon Manafort ‘‘would be unacceptable, and result in immediate, bipartisan action by Congress.’’

The Republican leaders of the Senate Judiciary Committee and the Senate and House intelligence committees were silent Monday about the significance of major developments in Mueller’s inquiry, as their Democratic counterparts called on Congress to increase their efforts.

But Mueller’s charges come as two of the three congressional investigations into Russian meddling have been foundering along political lines, with Republicans and Democrats pursuing separate and sometimes directly competing lines of inquiry.

Earlier this month, the House Intelligence Committee and the Senate Judiciary Committee launched inquiries into a deal approved by the Obama administration that gave Russia a significant stake in the American uranium market. That revived a political cudgel Trump used against Clinton during the presidential campaign, despite scant evidence of her personal involvement.

The Senate Judiciary Committee’s ranking Democrat, Senator Dianne Feinstein of California, also told reporters last week that she and the committee’s chairman, Senator Charles E. Grassley, an Iowa Republican, were going their separate ways on the panel’s Russia investigation.

They punctuated that announcement Friday by releasing a tranche of written requests for information from the White House, Trump’s personal attorney Michael Cohen, and the heads of social media companies caught up in Russia’s influence campaign.

‘‘Bob Mueller’s criminal investigation is important, but Congress has a responsibility to get to the bottom of this and work to make sure it never happens again,’’ Feinstein said Monday. ‘‘That’s why it’s so vital that the congressional investigations continue.’’

The charges in the Mueller investigation could complicate the committee’s ability to access key witnesses going forward, particularly Manafort. The Senate Judiciary Committee has struggled to secure an interview with Manafort in recent months.

Grassley’s team blames Feinstein for preventing the committee from interviewing him in July, before his apartment was raided by FBI agents. Feinstein has suggested Grassley has been slow-walking the committee’s inquiry and surmised to reporters that a drafted subpoena for Manafort’s testimony would not be issued.

The Judiciary Committee also has yet to mark up two bipartisan bills that would subject any effort to fire Mueller to a review by a panel of three federal judges. A spokesman for Grassley did not respond to a question about whether the committee would schedule a markup in light of the Manafort indictment.

Across the Capitol, House Speaker Paul D. Ryan, Republican of Wisconsin, did not comment on the substance of the indictments during an interview Monday morning with a Wisconsin radio station, except to promise that it would not affect the House’s rollout of a tax bill.

Representative Tom Cole, Republican of Oklahoma, who is close to Ryan, noted that the timing of the indictment and its ‘‘very serious’’ charges was ‘‘not particularly helpful’’ to the tax bill’s rollout and would probably make committees’ work harder.

‘‘My instinct tells me they’ve been threatened to some degree by the Mueller investigation — and appropriately so,’’ said Cole, who does not sit on any of the panels investigating Russian meddling.

But he refused to criticize Mueller’s inquiry, even pushing back on Trump’s criticism of it.

‘‘I don’t think they are on a witch hunt or it’s not fair,’’ Cole said of Mueller and his team.

House minority leader Nancy Pelosi, Democrat of California, meanwhile, stressed Monday that the developments in the Mueller investigation were an argument for appointing an independent commission to examine Russian meddling.

‘‘Even with an accelerating special counsel investigation inside the Justice Department, and investigations inside the Republican Congress, we still need an outside, fully independent investigation to expose Russia’s meddling in our election and the involvement of Trump officials,’’ Pelosi said.