WASHINGTON — In an extraordinary denunciation of Donald Trump’s temperament and competence, President Obama urged leaders of the Republican Party on Tuesday to withdraw their endorsements of Trump’s candidacy, flatly calling him “unfit to serve” as the nation’s 45th president.
Speaking in the East Room of the White House while Trump rallied supporters in a nearby Virginia suburb, the president noted the Republican criticism of Trump for his attacks on the Muslim parents of an American soldier, Captain Humayun Khan, who died in Iraq.
But Obama said the political recriminations from Republicans “ring hollow” if the party’s leaders continue to support Trump’s campaign.
“The question they have to ask themselves is: If you are repeatedly having to say in very strong terms that what he has said is unacceptable, why are you still endorsing him?” Obama said. “What does this say about your party that this is your standard-bearer?”
As the president made his comments, divisions in the GOP deepened. Trump’s unabashed and continuing hostility toward the Khans and his attacks on Republican leaders who have rebuked him for it threaten to shatter his uneasy alliance with the party.
Ignoring the pleas of his advisers and entreaties from party leaders, Trump has only dug in further. He told a Virginia television station he had no regrets about his clash with Khans. And in an extraordinarily provocative interview with the Washington Post, Trump declined to endorse for reelection several Republicans who had criticized him, including House Speaker Paul D. Ryan of Wisconsin and Senator John McCain of Arizona, who both face primaries this month.
He also belittled Senator Kelly Ayotte of New Hampshire, who criticized his treatment of the Khans, for not being supportive of his campaign.
For days, Trump’s top advisers and allies have urged him to move on from the feud, which erupted when Khizr Khan criticized him at the Democratic convention, and focus instead on the economy and the national security record of his Democratic opponent, Hillary Clinton. Yet, facing outcry on the left and right, Trump has insisted to associates that he has been treated unfairly by Khan, the news media, and some Republicans, said people familiar with the campaign’s deliberations who insisted on anonymity to discuss them.
Republicans now say Trump’s obstinacy in addressing perhaps the gravest crisis of his campaign may trigger drastic defections within the party, and Republican lawmakers and strategists have begun to entertain abandoning him en masse.
The president’s condemnation of Trump, and his direct appeal to Republicans to abandon their candidate, were stunning even in a city where politics has become a brutal and personal affair. Obama seemed eager to go beyond his past interventions in the race, which have included forceful rejections of Trump’s statements and policy proposals.
Douglas Brinkley, a presidential historian, called Obama’s comments “a highly unusual and almost unprecedented moment.” The last time a sitting president was as openly critical of the other party’s candidate, Brinkley said, was in 1953, when President Truman mocked Dwight D. Eisenhower as not knowing “any more about politics than a pig knows about Sunday.”
Using the formal backdrop of a joint news conference with Prime Minister Lee Hsien Loong of Singapore, Obama suggested that Trump would not abide by “norms and rules and common sense” and questioned whether he would “observe basic decency” should he reach the Oval Office.
The president said he would have been disappointed to lose in 2008 or 2012 but added that he had never doubted whether his Republican rivals, McCain and Mitt Romney, had the knowledge to make government work.
“That’s not the situation here,” Obama said.
As Obama condemned Trump, the Republican candidate repeatedly criticized Hillary Clinton and the president in an hour of remarks. He called Clinton a “liar” and a “thief” and said the country would be “finished” if voters choose four more years of a presidency like Obama’s.
Trump also accused Clinton of repeatedly lying when she told Chris Wallace on “Fox News Sunday” that James Comey, the FBI director, had said her statements about her private e-mails were truthful.
“I mean, she lied,” Trump said, prompting cries of “Lock her up!” from his supporters. “She, pure and simple, she only knows to lie. She really does. She only knows to lie. But she lied, and it’s a big story.”
Comey, testifying last month to Congress, said that “we have no basis to conclude she lied to the FBI.” But he also said that he could not say whether Clinton’s many public statements on the issue were truthful.
Trump had begun his remarks at his rally by saying that a veteran had given him a Purple Heart medal earlier in the day. “I always wanted to get the Purple Heart,” said Trump, who received five deferments from the draft during the Vietnam War. “This was much easier.”
Trump, in a written statement meant to respond directly to the president’s remarks, called Clinton “unfit to serve in any government office.” He also accused Obama and Clinton of allowing Americans to be slaughtered in Benghazi, Libya, letting veterans die waiting for medical care, and releasing immigrants into the United States to kill innocent people.
On Tuesday, retiring New York Representative Richard Hanna became the first Republican member of Congress to say he will vote for Clinton.
‘‘He is unfit to serve our party and cannot lead this country,’’ Hanna wrote in a column published in The Post-Standard newspaper of Syracuse. ‘‘He is unrepentant in all things.’’
Later, Hewlett-Packard executive Meg Whitman — a prominent Republican fund-raiser — threw her support behind Clinton, saying, ‘‘Donald Trump’s demagoguery has undermined the fabric of our national character.’’