JUDY WOODRUFF: Russian leaders, American generals, sensitive e-mails, and more, all of it the stuff of the presidential campaign over the past 24 hours.
John Yang has our report.
JOHN YANG: This morning, Hillary Clinton didn't even wait for her first campaign stop of the day, attacking Donald Trump before boarding her plane.
HILLARY CLINTON (D), Presidential Nominee: Last night was yet another test, and Donald Trump failed yet again. We saw more evidence that he is temperamentally unfit and totally unqualified to be commander in chief.
JOHN YANG: It was in response to the candidates' back-to-back appearances last night on an NBC News military forum. Trump was asked about Russian President Vladimir Putin's praise for him.
DONALD TRUMP (R), Presidential Nominee: If he says great things about me, I'm going to say great things about him. I have already said, he is really very much of a leader. I mean, you can say, oh, isn't that a terrible thing? He called — the man has very strong control over a country. Now, it's a very different system, and I don't happen to like the system.
But, certainly, in that system, he's been a leader, far more than our president has been a leader.
JOHN YANG: Today, that brought Clinton's strongest rebuke.
HILLARY CLINTON: That's not just unpatriotic and insulting for the people of our country, as well as to our commander in chief. It is scary.
JOHN YANG: Last night, a former Naval officer challenged Clinton about her handling of classified material.
MAN: How can you expect those such as myself who were and are entrusted with America's most sensitive information to have any confidence in your leadership as president when you clearly corrupted our national security?
HILLARY CLINTON: You know and I know classified material is designated. It is marked. There is a header, so that there is no dispute at all that what is being communicated to or from someone who has that access is marked classified. I communicated about classified material on a wholly separate system. I took it very seriously.
JOHN YANG: Another big topic at the forum was the fight against ISIS in Iraq and Syria. Clinton insisted she would never put ground troops into Iraq again. And Trump was asked about his claim that he knows more about ISIS than the generals.
DONALD TRUMP: The generals under Barack Obama and Hillary Clinton have not been successful.
MATT LAUER, NBC News: Do you know more about ISIS than they do?
DONALD TRUMP: I think under the leadership of Barack Obama and Hillary Clinton, the generals have been reduced to rubble. They have been reduced to a point where it's embarrassing for our country.
JOHN YANG: Half-a-world away, President Obama responded as he closed out his trip to Asia.
PRESIDENT BARACK OBAMA: I don't think the guy is qualified to be president of the United States. And every time he speaks, that opinion is confirmed.
And I think the most important thing for the public and the press is to just listen to what he says and follow up and ask questions about what appear to be either contradictory or uninformed or outright wacky ideas.
JOHN YANG: Foreign policy also figured prominently today for libertarian candidate Gary Johnson, though he may have wished it hadn't.
On MSNBC's "Morning Joe," he was asked about a much-discussed war-torn Syrian city.
MIKE BARNICLE, MSNBC: What would you do if you were elected about Aleppo?
GARY JOHNSON, Libertarian Presidential Nominee: About Aleppo. And what is Aleppo?
MIKE BARNICLE: You're kidding.
GARY JOHNSON: No.
MIKE BARNICLE: Aleppo is in Syria. It's the epicenter of the refugee crisis.
GARY JOHNSON: OK. Got it. Got it.
JOHN YANG: The long-shot candidate later said there was no excuse for the confusion.
For the "PBS NewsHour," I'm John Yang.