WASHINGTON — President Trump was watching television in the White House on Wednesday morning when cable news channels started airing Speaker Nancy Pelosi and Representative Adam B. Schiff, the chairman of the House Intelligence Committee, warning at a news conference that any attempts by the president to stonewall their impeachment investigation would be viewed as obstruction.

Mr. Trump did not wait for Ms. Pelosi and Mr. Schiff to finish before responding. First he attacked Ms. Pelosi on Twitter, saying she was neglecting the work of Congress “and trying to win an election through impeachment.” Then he tweeted again, sharing a campaign video that accused Democrats of trying to undo the results of the 2016 election.

He continued those attacks later in the afternoon, both before and after a meeting with Sauli Niinisto, the president of Finland, and became increasingly angry as he went on.

Mr. Trump has long believed that he is the best communicator in the White House, but as the presidential campaign picks up its pace and the prospect of his impeachment becomes more real, he seems to be its only empowered communicator, a one-man war room responding to developments almost hour by hour. And that is making many Republicans anxious.

For now, the White House has no organized response to impeachment, little guidance for surrogates to spread a consistent message even if it had developed one, and minimal coordination between the president’s legal advisers and his political ones. And West Wing aides are divided on everything from who is in charge to whether, after two years of the investigation by the special counsel, Robert S. Mueller III, impeachment even poses a serious political threat to the president.

“This is a very different animal than the Mueller investigation,” said Josh Holmes, a former top aide to Senator Mitch McConnell of Kentucky, the majority leader. “It’s a political question, not a legal one. They need to persuade Republicans in the House and the Senate of a bunch of really good arguments to have the partywide insulation the president is going to prefer going into this fight.”

And the White House has a narrow runway to adjust and tighten its response, with just over a week until the congressional recess ends. At that point, Republicans will return from their home districts and face questions about Mr. Trump’s tweets and condemnation of the whistle-blower — questions they might have difficulty answering.

“At this point, the president can hold his own,” Mr. Holmes added. “But I think they should be concerned with how Republicans handle it when they get back and for that, it probably does take a little bit of structure.”

For weeks, the most visible defender of the president has been Rudolph W. Giuliani, Mr. Trump’s personal lawyer, who is himself a central figure in the allegations that Mr. Trump pressured the Ukrainian government to find dirt on Democrats, leading several of the president’s advisers to warn that Mr. Giuliani’s freelance television appearances do him more harm than good.

But Mr. Trump has told them that he is pleased with the performances, and spent part of Saturday giving Mr. Giuliani talking points for the Sunday show circuit.

Others have urged the president to tone down his language, including his repeated use of the word “treason.” But Mr. Trump, who has frequently abandoned norms and paid little in terms of personal political consequences for doing so, has not changed his behavior. That has led some advisers, like Mick Mulvaney, the acting White House chief of staff, to settle into a hands-off approach. Mr. Mulvaney told associates he spent part of Sunday on a golf course outside Washington.

What’s left is Mr. Trump acting alone, and poised to live-tweet his own impeachment, complete with all-caps obscenities, alarming accusations of treason and warnings that impeachment is really a “coup.”

During his public appearances with Mr. Niinisto on Wednesday, Mr. Trump seemed as riled up as he has at any point in his presidency, railing against his opponents, mangling the facts to fit his preferred narrative and making allegations without evidence. Flush with anger and gesturing sharply, he spent most of his time on offense attacking his critics using words like “lowlife,” “dishonest,” “corrupt,” “shifty” and “fraud.”

Behind the scenes, Mr. Trump has seesawed from projecting confidence that there is a political benefit from the impeachment fight to lashing out at aides, blaming them for the fact that he is entangled by it in the first place.

“We have stated this several times,” she said. “There has not been any effort to put together a war room. The president did nothing wrong and we are still working over here.”

The confusion in the White House is leaving conservatives who want to help support Mr. Trump without a clear road map for how to do so. At a meeting on Wednesday morning with conservatives and Capitol Hill aides, White House officials were still taking the temperature on the potential political fallout of impeachment, rather than offering any instructions about their path going forward.

Paul Teller, an aide in the White House Office of Legislative Affairs, quizzed the group about whether it thought a long or short impeachment process would play better with the president’s base. Mr. Teller also told the group that he believed Mr. Trump would want to see Mr. McConnell bring impeachment to a vote on the Senate floor, where Mr. Trump would be acquitted, rather than move to simply dismiss the charges.

Stephen Miller, Mr. Trump’s main domestic policy adviser, also briefly attended the meeting, but observed more than he spoke, according to a person familiar with what took place.

In the West Wing, aides who have seen Mr. Trump survive potentially debilitating scandals like the release of the “Access Hollywood” tape a month before the 2016 election, and the appointment of a special counsel with wide-ranging powers to investigate him, are shrugging off impeachment as just another bump in the road.

Jared Kushner, the president’s son-in-law and a senior White House adviser, is not pushing for the creation of any sort of official “war room,” and has told colleagues he is comfortable with the current structure supporting the president — one that also gives him freewheeling power.

Kellyanne Conway, the White House counselor and one of Mr. Trump’s longest-serving aides, has told reporters that Trump supporters will not leave him because of impeachment. She joins a group that includes Jay Sekulow, one of the president’s personal lawyers, and other aides and allies, who believe that anything resembling a White House “war room” is needless and would make them look as if they were under siege.

“We won the Mueller probe,” Mr. Sekulow said on his afternoon radio show on Monday. “I tell you what. If Mueller was a war, this is a skirmish.”

But on Wednesday night, one White House official was anticipating changes with some staff members focused on the inquiry.

Other aides privately conceded that they did not know how the politics of the impeachment process would play out, and would like to see the White House Counsel’s Office bring back someone like Emmet T. Flood, the White House lawyer who oversaw the administration’s response to the special counsel’s investigation and worked on President Bill Clinton’s legal team during his impeachment.

Mr. Flood left the administration in June.

Some are also starting to notice small public cracks in Republican support.

“Starting to encounter Republicans who wonder if maybe the President should step aside for Pence,” Erick Erickson, the conservative blogger and radio host, wrote on Twitter on Tuesday. “They’re absolutely in the minority on the GOP side, but there does seem to be a fatigue setting in — tired of always fighting and always having to defend.”

While Mr. Trump has been focused in recent days on defending himself, his advisers have continued the assault on Joseph R. Biden, Jr., the former vice president and current presidential candidate, hoping it will cut through the impeachment noise. Mr. Kushner, who has been overseeing campaign messaging on impeachment, also personally signed off on a new round of campaign ads attacking Mr. Biden and his son Hunter Biden.

Mr. Trump insisted on Wednesday that he was not trying to damage Mr. Biden in order to knock him out of the race — even while he attacked him.

“I’d rather run against Biden than almost any of those candidates,” he told reporters. “And I think they’re all weak, but I think Biden has never been a smart guy and he’s less smart now than he ever was.”