The dismissal added another volatile element to the partisanship engulfing the capital and raised the prospect of another confirmation fight in the Senate.
WASHINGTON — President Trump’s stunning firing of the F. B. I. director, James B. Comey, injected another volatile ingredient into the partisanship already engulfing the capital and threatened to overwhelm Republican efforts to turn their government control into legislative success.
The decision to replace Mr. Comey also increased the prospect of another contentious confirmation fight in the Senate as Mr. Trump promised to move quickly to replace the director, who had overseen the inquiry into Russian meddling in the election. And the White House handling of the dismissal — and its apparent failure to anticipate the severe backlash the move generated — renewed questions about the competency of administration officials and their ability to navigate Washington.
Already on the defensive over their health care proposal, congressional Republicans suddenly found themselves trying to explain how Mr. Trump was within his rights in jettisoning Mr. Comey. Democrats quickly coalesced around the push for a special prosecutor to take control of the inquiry, saying the leadership of the Justice Department could not be trusted with the job after the termination of the F. B. I. chief on what they considered spurious grounds.
“Clearly the time is now for an independent prosecutor, ” Senator Christopher Murphy, Democrat of Connecticut, said Wednesday. “The Senate, designed by the founding fathers as the guardian of democratic norms, must now rise to meet the gravity of this moment.”
To emphasize that gravity, Senator Chuck Schumer of New York, the Democratic leader, summoned his colleagues to sit at their desks as the Senate convened Wednesday morning to take in whatever the majority leader, Senator Mitch McConnell, Republican of Kentucky, had to say about the firing.
Mr. Schumer also requested that Mr. McConnell call a closed-door and possibly classified all-senators briefing with top Justice Department officials on the state of the investigation. Such a session could underscore what Democrats view as the seriousness of the president’s decision and give senators in both parties a private opportunity to confront their differences.
But if Democrats were hoping that the uproar surrounding the firing was going to push Mr. McConnell in their direction, they were badly mistaken.
Although other senior Republicans expressed some misgivings about the firing, the majority leader showed no sign of budging or joining a call for a special prosecutor. Instead, he said that any new investigation would only impede current inquiries being conducted by the House and Senate intelligence committees and the F. B. I. He noted that Democrats and Mr. Schumer himself had made clear their dissatisfaction with Mr. Comey over the inquiry into Hillary Clinton’s email practices during the presidential campaign.
“This is what we have now, ” Mr. McConnell said, “our Democratic colleagues complaining about the removal of an F. B. I. director whom they themselves repeatedly and sharply criticized.”
Mr. McConnell also issued a veiled warning to Democrats who are likely to try to use any confirmation hearing for a new F. B. I. director to air their grievances about the firing and push for a special prosecutor if one is not in place by then. He said Senate Republicans anticipated a “full, fair and timely” confirmation of the person selected by Mr. Trump to take over the agency.
But Democrats were already setting the stage for a confirmation showdown. “The Senate must stand firm, ” Senator Michael Bennet, Democrat of Colorado, said in a Wednesday post on Twitter. “We will only confirm an FBI director who pledges a vigorous investigation of Russian interference & connections.”
Despite Mr. McConnell’s efforts to move past the firing, Democrats and some Republicans are going to be unwilling to do so. Senator Rob Portman, Republican of Ohio, on Wednesday joined some of his colleagues in challenging the White House explanation for the firing.
“Given the timing and circumstances of the decision, I believe the White House should provide a fuller explanation regarding the president’s rationale, ” he said.
Democrats view this as an opportunity to force the appointment of a special prosecutor they have sought since serious questions were first raised about Russian meddling in the election. They have, at least for the moment, relegated their push for a special congressional committee or independent commission to the back seat.
Though most Republicans continued to oppose the idea, some small cracks in the resistance were giving Democrats hope that they could prevail while at the minimum forcing Republicans to defend their opposition to the public.
The fight is likely to spill over into the consideration of Trump administration nominees to the federal bench — which the White House initiated this week with the announcement of a slate of conservative judges and is one area where the administration could have some success.
Though Democrats can keep public pressure on Republicans over the firing, their minority status limits their ability to force action. They can slow the Senate to a crawl, as they tried to do Wednesday by refusing to give consent to the Senate holding a daylong slate of hearings. But changes in Senate practices instituted by Democrats in 2013 mean that a new F. B. I. director can ultimately be put in office on a straight majority vote.
Still, the firing presented a formidable new distraction for a White House and congressional Republicans who were already struggling badly to deliver on their pledge to enact a conservative agenda. They already faced opposition Democrats with little trust in the president’s motives or intentions. The sudden departure of Mr. Comey only made a bad situation much worse.
