WASHINGTON — The disclosure that President Trump asked the F.B.I. director, James B. Comey, to back off an investigation of Michael T. Flynn intensified calls for more aggressive investigations and a special counsel from many quarters, except the most important one — top congressional Republicans.
The revelation, based on contemporaneous notes kept by Mr. Comey, heightened the unease among Republicans on Capitol Hill and produced new calls for Mr. Comey to testify. But it did not seem to stir Republican leaders to any new level of urgency. Their position has puzzled Democrats, political analysts and many in the news media who keep asking: What will it take for leading Republicans to abandon Mr. Trump given the escalating White House chaos and its impact on the policy agenda?
But as they survey the political and investigative landscape, Republicans say they have good reasons for not being swept up in what they see as the self-inflicted disorder rocking Mr. Trump and his White House.
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Here are some of them.
No Evidence of Collusion
Top Republicans on and off the Senate Intelligence Committee say they have yet to see convincing evidence of Mr. Trump colluding with the Russians during the presidential campaign, despite the intense scrutiny. Without such proof, Republicans are reluctant to engage in undermining Mr. Trump.
A paper trail or other intelligence showing such collusion could abruptly change their position, given that Republicans such as Senator Mitch McConnell of Kentucky, the majority leader, see Russia as a dangerous adversary.
House and Senate Republicans say that the inquiries being conducted by the intelligence committees and other panels are more than sufficient and capable of producing results.
Even Democrats have credited Republican leaders of the panels with conducting serious, credible investigations, though not at the pace they would like.
Republicans say that a special counsel could complicate their inquiries. “I don’t see that happening,” Senator John Barrasso of Wyoming, a member of the Republican leadership, said Tuesday.
Rejecting Democrats’ Demands
Republicans are loath to accede to Democratic demands of any kind. What is the point of being in control of the House and Senate if they are going to acquiesce to heated Democratic cries for a special counsel or a select committee?
In their eyes, Democrats are devoted to stirring up resistance to the new White House to stymie the president and his party as they finally get to enact their tax and budget priorities. They won the elections in November and are in charge, not Senator Chuck Schumer of New York, the Democratic leader.
Protecting the Base
Republicans are acutely aware that if they turn on Mr. Trump, they run the risk of alienating the voters who made him president, voters the Republican Party is going to badly need in the midterm elections.
While Democrats and growing numbers of independent voters are digging in against Mr. Trump, conservatives in red states that provide the party majorities in the House and Senate are still standing by him. It is the same reasoning behind the Republican push for their health care bill — they need to mollify the base even at the risk of alienating other voting blocs.
Distrust of the Media
Republicans distrust many in the news media and see it as an institution that has decided to undermine an outsider president in return for website clicks and subscriptions.
They see news organizations working in concert with forces actively seeking to derail if not destroy the first Republican administration in eight years. Speaker Paul D. Ryan echoed that theme on Wednesday.
“It is obvious there are some people out there who want to harm the president,” he told reporters.
Trump Is Delivering
Like many of the voters in their states and districts, congressional Republicans are happy with the steps being taken by the Trump administration on immigration, crime, trade and deregulation. They see the president through an entirely different lens than that of his fierce critics.
“He’s an outsider in this process as I am, and I will tell you I give him high marks in the first four months in office,” Senator David Perdue, Republican of Georgia and a Trump ally, told Fox News on Tuesday. “This is a president that is beginning to reassert the national interests of America.”
Fear of a Special Counsel
Republicans remain skeptical that agreeing to a special counsel would in any way lower the temperature on the controversy raging around the White House.
Instead, they worry that moving in that direction might only inflame the situation, giving new credibility to accusations around Mr. Trump and others and possibly dragging the inquiry into the midterms and beyond, with Republicans having little control over the pace or the outcome.
Republicans, given their own experience with Bill and Hillary Clinton, are well aware of how special inquiries can have a long and seemingly endless reach.
We Can Do It Ourselves
Last month’s spending deal showed that congressional Republicans can circumvent the president to produce legislation. They seem to be moving in that direction again, ignoring more administration calls for budget cuts and working out tax and health care deals internally. If they have to produce without the president, they will try to do so.
All of this is not to say that there is no tipping point for Republicans when it comes to Mr. Trump, and they may be getting closer. Republican officials say new developments and substantiation of the Comey claims could prove devastating.
But Mr. Ryan reaffirmed his party’s posture on Wednesday, saying that “before rushing to judgment” the Republican-led Congress would “get all the pertinent information.”
“Our job is to be responsible, sober and focused only on gathering the facts,” he said.
The interests of congressional Republicans and Mr. Trump remain too closely aligned for a major rupture. Until that relationship changes, the view of most Republicans will not change.