JUDY WOODRUFF: A presidential broadside today aimed at Donald Trump. President Obama took on the man who is running to succeed him in his strongest terms yet.
PRESIDENT BARACK OBAMA: I think the Republican nominee is unfit to serve as president. I said so last week, and he keeps on proving it.
JUDY WOODRUFF: The rebuke came at a news conference with the visiting prime minister of Singapore. The president drew a sharp distinction between Donald Trump and the Republican nominees he had faced, John McCain and Mitt Romney.
PRESIDENT BARACK OBAMA: I never thought that they couldn't do the job. And had they won, I would have been disappointed, but I would have said to all Americans, they are — this is our president and I know they are going to abide by certain norms and rules and common sense, will observe basic decency.
JUDY WOODRUFF: All of this followed Trump's repeated criticisms of Khizr and Ghazala Khan, parents of a U.S. army officer who died in Iraq.
Republican leaders condemned the remarks, but Mr. Obama said that's not enough.
PRESIDENT BARACK OBAMA: This is daily and weekly where they are distancing themselves from statements he's making. There has to be a point at which you say, this is not somebody I can support for president of the United States.
JUDY WOODRUFF: One New York Republican congressman, Richard Hanna, did just that today.
In a newspaper opinion columnist, he wrote: "Mr. Trump has attacked the parents of a slain U.S. soldier. Where do we draw the line? While I disagree with her on many issues, I will vote for Hillary Clinton."
Trump was speaking in Northern Virginia as the president held his news conference, and he made no mention of the Obama criticism or the Khans. But it was in the air just the same.
DONALD TRUMP (R), Presidential Nominee: A man came up to me and he handed me his Purple Heart.
JUDY WOODRUFF: The Purple Heart, given to those wounded or killed in action, came from a retired lieutenant colonel.
DONALD TRUMP: I always wanted to get the Purple Heart. This was much easier.
JUDY WOODRUFF: Later, Trump did answer the president in a statement, charging he and his former secretary of state betrayed American security and American workers.
And Trump declared — quote — "Hillary Clinton has proven herself unfit to serve in any government office."
Trump supporters at the rally appeared unfazed by the latest blowup.
DALE NYLEC, Trump Supporter: The coverage is just insane. I think they make a big deal about that. First of all, he was speaking from his heart. And he wasn't accusing them or saying anything.
JUDY WOODRUFF: Trump moves on to campaign in Florida tomorrow. Clinton will be in Colorado.
Also today, Donald Trump told The Washington Post he is not ready to endorse Republican House Speaker Paul Ryan for reelection. He also said he won't support Republican Senators John McCain and Kelly Ayotte for new terms.