ALISYN CAMEROTA (HOST): David, let's talk about President Obama and Hillary Clinton going after Donald Trump, and Donald Trump returning the criticism. So how unusual is it for a president, a sitting president, to be weighing in on the presumptive Republican nominee in this fashion?
DAVID GREGORY: Well I don't think it's terribly unusual. We haven't been in a situation where you've had a president doing that this directly, but I think President Obama feels that, of course, it's his legacy that's being attacked here in terms of his approach to terrorism. This is from a candidate in Donald Trump who has questioned whether President Obama was even born in the United States and is a Muslim. He was born in the United States. He is not a Muslim. And yet it was Donald Trump who has spun this web of conspiracy and lies now for a number of years. So I think President Obama takes it seriously and I think he thinks there's high stakes involved with this debate. In effect, he's acting as a running mate for Hillary Clinton here by being incredibly forceful on this point, and there's a lot of cover here for President Obama, because Donald Trump in his prescriptions for how to fight terrorism and how to respond to something like this seems to be really hurting himself. Doubling down on a Muslim ban, which no Republicans support. Particularly Republican leaders. And striking a tone that frankly is at odds with other Republican leaders. So he doesn't seem to be gaining ground within the Republican establishment, even if there are some people who hear this, who are supporters of his, who say, “Yeah, right on.”