WASHINGTON — During a discussion about his party’s legislative high points this year with a small group at the U.S. Chamber of Commerce last week, Senator Mitch McConnell, the majority leader, expressed a new concern about an old habit of President Trump’s.
The many “distractions” generated by the president, Mr. McConnell said during the dinner, were preventing Republicans from having a coherent message for the midterm elections focused on the booming economy, according to multiple people who were briefed on the remarks.
Representative Paul D. Ryan, the House speaker, who also attended, expressed another concern — that the president’s talk with his supporters of a “red wave” in November was unfounded. All agreed that he should instead be sounding the alarm about the possibility of big Democratic gains.
The two congressional leaders were only echoing the worries of many Republican strategists and Mr. Trump’s own advisers.
They say these “distractions” — everything from the president’s angry response to criticism about hurricane relief efforts in Puerto Rico to his continuing willingness to do battle with any number of opponents on Twitter — mean that Republican candidates spend too much time answering questions about what the leader of their party is saying or tweeting instead of focusing on the economic news that should be the real story of the election.
And Mr. Trump’s confidence in inevitable Republican success, they say, has prevented him from focusing on the need for a coherent message, and his own supporters from understanding the very real possibility that Democrats could retake the House and even the Senate.
A spokesman for Mr. Ryan did not respond to an email seeking comment about the speaker’s remarks at the chamber, and Antonia Ferrier, a spokeswoman for Mr. McConnell, said this account of what the majority leader said was “inaccurate.”
But in the last week, Mr. Trump seems to have heeded some of the warnings, forging common cause with Senate Republicans to work toward the confirmation of Judge Brett M. Kavanaugh to the Supreme Court. In a pleasant surprise to Mr. Trump’s aides and Republicans on Capitol Hill, the president avoided attacking Judge Kavanaugh’s accuser, and endorsed a Senate hearing where the allegations could be aired.
But that discipline did not fully hold. On Wednesday, Mr. Trump expressed sympathy for Judge Kavanaugh’s family rather than the woman who says she was abused by him when they were teenagers. He complained in an interview that “I don’t have an attorney general.” He also demanded funding for the border wall — another topic many Republican leaders would rather avoid heading into the midterms.
Republican pollsters have reinforced the concerns of the party’s congressional leaders that the White House is not always helping when it comes to the midterms.
“They have spent way too much time yelling about investigations and not enough time educating about the economy,” Frank Luntz, a longtime Republican pollster, said in an interview. The president, he added, “deserves a lot more credit than he has been given, but he’s also somewhat responsible because he hasn’t been so focused and attentive to the changes that have really happened” in the economy.
Neil Newhouse, another pollster, has made clear his worries that too many Republicans are taking the midterms for granted.
“We need to make real the threat that Democrats have a good shot of winning control of Congress,” he said in a presentation for the Republican National Committee at the end of August that was recently shared with the president.
Voters who are not die-hard Trump supporters may not “believe there’s anything at stake in this election,” Mr. Newhouse wrote. “Put simply, they don’t believe that Democrats will win the House. (Why should they believe the same prognosticators that told them that Hillary was going to be elected president?).”
Mr. Trump has alternately acknowledged to aides and supporters that the climate is troublesome and insisted that the worst will never happen. It is not clear that he actually believes his talk of a “red wave,” or if he is trying to will it into existence, advisers and allies say.
But the potential for an electoral disaster on Nov. 6 has certainly not been lost on White House officials, who say it has added to existing anxiety about what will come next in the president’s term. According to interviews with over half a dozen current and former White House aides and campaign officials, they are girding for the possibility of a political landscape — and, possibly, a West Wing — that could look very different after Election Day.
“This is a White House that is achieving very large things,” Newt Gingrich, the former speaker of the House, said in an interview, but “sometimes in very clumsy ways.”
“I believe the president understands that this midterm is hard,” Mr. Gingrich said, “that historically the midterm is against him, but that it’s doable.”
The president’s aides are trying to focus Mr. Trump on the next seven weeks by painting a picture of what it would look like if Democrats retook the House — an avalanche of subpoenas, a halt to his legislative agenda and, potentially, an impeachment proceeding.
Other aides — some of whom were in elementary school the last time a president was impeached — have started listening to “Slow Burn,” a podcast about the events surrounding the Nixon and Clinton impeachments.
Mr. Gingrich said that the White House was likely to be preparing to play defense against the House and offense with the Senate.
“They raise the 2020 campaign on ‘what future do you want?’” Mr. Gingrich said. “Sanctuary cities could be the future. You too could have an MS-13 gang in your neighborhood.”
Even as the White House looks to keep the president’s focus on the election’s final stretch, officials there recognize the risks to their own job security. Many anticipate a potential wipeout of the West Wing staff if things go badly, given that Mr. Trump often blames aides for any of his troubles.
Some of the president’s closest aides in the West Wing remain wary of the influence of outside advisers to the president, particularly Corey Lewandowski and David Bossie, former campaign advisers who still have contact and influence with the president.
Mr. Lewandowski and Mr. Bossie are planning to publish a book three weeks after the midterms. The timing has provoked anxiety among some Trump aides, who worry it will be explicit in assigning blame to the White House political operation and other advisers if Republicans lose badly.
Four advisers to the president said they saw the book and its title — “Trump’s Enemies: How the Deep State Is Undermining the Presidency” — hanging over them as the midterms approach. Officials close to Ronna McDaniel, the party chairwoman, say that some of those close to Mr. Trump have begun to agitate for a change in leadership if there are significant midterm losses.
“Our book is not a problem for anybody who’s not an enemy of the president,” Mr. Lewandowski said.
In a recent interview with the radio host John Fredericks, Mr. Lewandowski made clear that he believes the president has been ill-served by those who were characters in “Fear,” Bob Woodward’s book about dysfunction in the Trump White House.
“He’s fighting his own staff,” Mr. Lewandowski said, adding that he hoped for a “wholesale fundamental change” inside the White House.