WASHINGTON - President Barack Obama on Tuesday escalated his criticism of Donald Trump, calling him "unfit to serve as president," as the Republican presidential nominee faced censure from members of both parties for disparaging the parents of a fallen U.S. Army captain.
"The notion that he would attack a Gold Star family that made such extraordinary sacrifices on behalf of our country, the fact that he doesn't appear to have basic knowledge around critical issues in Europe, in the Middle East, in Asia, means that he is woefully unprepared to do this job," Obama said at the White House, during a news conference with the prime minister of Singapore.
Obama challenged Republican leaders to stand up to Trump, saying their condemnations "ring hollow," as long as they still pledge to vote for him.
"There has to come a point at which you say, 'Enough,' " the president said.
The rebukes to Trump this week have been bipartisan and among the most sustained of the election cycle.
They have mainly been a response to Trump's denigration of Khizr and Ghazala Khan, immigrants from Pakistan who appeared last week at the Democratic National Convention to denounce Trump for his harsh rhetoric about Muslims, saying their son, who was killed in Iraq, would have been barred from entering the country under Trump's proposed ban.
But the broadsides also have focused on the nominee's comments about foreign relations, including his apparent ignorance of Russia's annexaton of the Ukrainian territory of Crimea in 2014 and his appeal to Russian actors to expose Democratic presidential nominee Hillary Clinton's emails.
In response, Trump has laughed off concerns about his overtures to Russian President Vladimir Putin, saying warmer relations would help the United States pursue its international objectives, such as defeating Islamic State militants.
At a campaign event Tuesday in Ashburn, Virginia, Trump attacked Clinton for having a poor relationship with Putin, saying, "This is a nuclear country we're talking about. Russia. Strong nuclear country."
"Their stuff is newer ... they have a lot more," he said. "She wants to play the tough one. She's not tough."
Meanwhile, a Kremlin spokesman told NBC News this week that Putin has never had any contact with Trump, which is in line with a recent statement by Trump that he has not spoken to Putin - and yet in direct conflict with the real estate mogul's prior declarations, including at the National Press Club in 2014, when Trump said he had been in Moscow and had spoken, "indirectly and directly," with the Russian president.
In his hour-long remarks on Tuesday, delivered at a local high school, Trump repeated his grave warnings about immigration - across the Southern border from Mexico, as well as from countries beset by Islamic radicalism. Because "we don't know if they're ISIS," Trump said of migrants from the Middle East, the result would be "the all-time great Trojan horse."
He didn't mention the Khans, who have proven themselves dogged in their campaign against Trump, or new evidence that the candidate's approach is driving a wedge in the Republican Party.
Rep. Richard Hanna, R-N.Y., on Tuesday became the first sitting Republican member of Congress to say publicly that he plans to vote for Clinton, declaring in an interview with Syracuse.com that Trump is a "national embarrassment."
The three-term congressman, who represents a swath of upstate New York near Syracuse but is not running for re-election this year, has bucked his party in the past on issues ranging from gay marriage to climate change. He declared his support for Clinton in an opinion piece published Tuesday on the news website and elaborated in an interview that Trump's continued feud with the parents of a Muslim-American Army captain killed in Iraq were the final straw.
"I saw that and felt incensed," Hanna said in the interview. "I was stunned by the callousness of his comments."
He added: "I think Trump is a national embarrassment. Is he really the guy you want to have the nuclear codes?"
Hanna already has said he will not support Trump - a stance shared by a handful of his Republican colleagues - but his pronouncement that he would support Clinton, a woman reviled by much of his party, dealt yet another blow to Trump as his campaign struggles under mounting bipartisan criticism over his response to the Khans, whose son, Humayun, was killed in 2004, at age 27, by a car bomber in Iraq.
Trump said Khizr Khan had "no right" to assail him as he did in the speech at the Democratic convention, in which he encouraged the businessman to read the Constitution. He also suggested that Ghazala Khan was not permitted to speak at the convention because she is Muslim.
"In his latest foray of insults, Mr. Trump has attacked the parents of a slain U.S. soldier," Hanna wrote. "Where do we draw the line? I thought it would have been when he alleged that U.S. Senator John McCain was not a war hero because he was caught. Or the countless other insults he's proudly lobbed from behind the Republican presidential podium. For me, it is not enough to simply denounce his comments: He is unfit to serve our party and cannot lead this country."
Trump has refused to stand down, tweeting Monday morning that Khan had "viciously attacked" him and had shifted focus from the real concern, "RADICAL ISLAMIC TERRORISM."
In response to his repeated swipes against the Khans, a bipartisan group of decorated combat veterans, members of Congress and family members of slain soldiers on Monday scolded Trump for clashing with the parents of a fallen soldier.
A particularly lengthy and impassioned rebuke came from McCain, the Senate Armed Services Committee chairman and an Arizona Republican who was a prisoner of war in Vietnam.
"While our party has bestowed upon him the nomination, it is not accompanied by unfettered license to defame those who are the best among us," McCain said.
At Tuesday's Ashburn campaign event, though, Trump said a man approached him and handed him a Purple Heart medal, which is presented to soldiers wounded in combat. Trump told the crowd at his rally that he has "always wanted to get the Purple Heart."
"I said to him, 'Is that, like, the real one or is that a copy?' " Trump recounted. "And he said, 'That's my real Purple Heart. I have such confidence in you.' And I said, 'Man! That's like, that's like big stuff.' "
"I always wanted to get the Purple Heart. This was much easier," continued Trump, who has never served in the armed forces. "But I tell you, it was such an honor."
The veteran, Lt. Col. Louis Dorfman, declined Trump's invitation to speak at Tuesday's town hall meeting.
Another blow to Trump came when Sally Bradshaw, a longtime adviser to Jeb Bush and an architect of the GOP's attempt four years ago to court younger, more diverse voters, fled the Republican Party this week. She said she would vote for Clinton if the race in her home state of Florida ends up being close.
"This is a time when country has to take priority over political parties. Donald Trump cannot be elected president," she told CNN.
Neither departure - Hanna's nor Bradshaw's - necessarily signals faltering support among voters drawn to Trump, in part, because of his strident rhetoric and willingness to eschew political decorum in favor of a tough stance on immigration and national defense.
Yet they show that Trump's delicate alliance with party leaders, rather than improving as the campaign wears on, is continuing to fray.
The desertions also reveal the painful internal divide over how the party should handle a nominee with little apparent loyalty to other Republicans. On Monday, for instance, Trump tweeted words of thanks to Paul Nehlen, who is challenging House Speaker Paul Ryan in the Republican primary in his Wisconsin House district this month.
Meanwhile, Trump's numbers have taken a dive in polls conducted following both political conventions. A CBS poll found a four-point bump for Clinton, who now enjoys a 46-39 lead over her Republican opponent, while a CNN/ORC survey showed the Democratic nominee with a 7-point bump and a 52-43 lead over Trump.
The Associated Press contributed to this report.