At a White House event Thursday afternoon, Trump said, "She's a mess," called Pelosi "crazy Nancy" and said "she's lost it."
"I have been watching her for a long period of time. She's not the same person. She’s lost it," Trump said, in a flurry of increasingly personal attacks on his political nemesis.
"It was sad when I watched Nancy all moving, the movement and the hands and the craziness. I watch that, by the way, a person that has some problems," he added, appearing to refer her news conference earlier in the day.
Trump went around the room asking Counselor Kellyanne Conway, press secretary Sarah Sanders and other top aides to testify about how calm he was in a White House meeting on Wednesday with Pelosi and Senate Minority Leader Chuck Schumer that he left abruptly after just three minutes.
The president, as he's done before, referred to himself as "an extremely stable genius."
Pelosi, using his words, tweeted back almost immediately.
"I don't think anyone wants to be impeached," Trump also said, referring to Pelosi's claim that he was trying goad Democrats into starting an impeachment inquiry.
Earlier Thursday, Pelosi appeared emboldened by Wednesday's fracas, capitalizing on the showdown to move past her party’s growing divisions regarding the prospect of impeaching the president.
“He pulled a stunt,” Pelosi, D-Calif., told reporters at a news conference in the Capitol. "The president has a bag of tricks and the White House has a bag of tricks that they save for certain occasions. They don't necessarily apply to the occasion, but they're a distraction."
Pelosi said she believes the president wants congressional Democrats to launch an impeachment inquiry prematurely, which could doom Democrats in the eyes of an electorate that watches with curiosity.
"What really got to him was these court cases and the House Democratic Caucus has not passed impeachment and that’s where he wants us to be," she said.
Pelosi said that Trump's behavior "in terms of his obstruction of justice," including ignoring congressional subpoenas "could be impeachment offenses."
"We want to follow the facts to get the truth to the American people," she said. "How we deal with [impeachment] is a decision that our caucus makes, and our caucus is very much saying whatever we do, we need to be ready when we do it."
But Pelosi made clear that impeachment is still premature, and potentially "a very divisive place to go in our country."
"We can get the facts to the American people through our investigation. It may take us to a place that is unavoidable in terms of impeachment or not," she said. "But we're not at that place."
Pelosi said she continues to pray for Trump, and believes he needs "an intervention."
“Now this time, another temper tantrum,” she said. "I pray for the president of the United States. I wish that his family or his administration or his staff would have an intervention for the good of the country."
Even though the president has ruled out cooperating on advancing bipartisan legislation until Democrats end their investigations into him and his administration, Democrats insist they are committed to salvaging an infrastructure package and stand ready and willing to work with Trump.
Pelosi’s decision to accuse Trump of a “cover-up” Thursday infuriated the president, but the speaker emphasized it was not the first time she had suggested his conduct amounted to a cover-up, and she claimed she did not intend to provoke Trump into an outburst that has all but ended any fleeting prospect of bipartisanship. Instead, she believes Trump "wasn't up to the task of figuring out the difficult choices of how to cover the cost of the important infrastructure legislation."
"There's a question of the American people understanding that what he's doing is an assault on the Constitution of the United States," Pelosi said, justifying her caucus's widening investigations. "We can walk and chew gum at the same time. I hope he can, too."
"Whether it's the crisis at the border, whether it's infrastructure, or anything else. It's very hard to have a meeting where you accuse the President of the United States of a crime and then an hour later show up and act as if nothing's happened. The idea of that is insane," Sanders told reporters Thursday morning.
"The president's feelings weren't hurt. She accused him of a crime. Let that sink in," Sanders said. "She didn't say I don't like you. She accused him of committing a crime."
ABC News' Katherine Faulders contributed to this report.