"How can you be shocked?" he asked to laughter from the crowd, according to a transcript. "This is the guy, remember, who was sure that I was born in Kenya - who just wouldn't let it go. And all this same Republican establishment, they weren't saying nothing. As long as it was directed at me, they were fine with it. They thought it was a hoot, wanted to get his endorsement. And then now, suddenly, we're shocked that there's gambling going on in this establishment."

"What is happening in this primary is just a distillation of what's been happening inside their party for more than a decade. I mean, the reason that many of their voters are responding is because this is what's been fed through the messages they've been sending for a long time - that you just make flat assertions that don't comport with the facts. That you just deny the evidence of science. That compromise is a betrayal. That the other side isn't simply wrong, or we just disagree, we want to take a different approach, but the other side is destroying the country, or treasonous. I mean, that's - look it up. That's what they've been saying."

Donald Trump just capitalisd on the GOP's own tactics, Obama argues. Credit:AP

"So they can't be surprised when somebody suddenly looks and says, you know what, I can do that even better. I can make stuff up better than that. I can be more outrageous than that. I can insult people even better than that. I can be even more uncivil. I mean, conservative outlets have been feeding their base constantly the notion that everything is a disaster, that everybody else is to blame, that Obamacare is destroying the country. And it doesn't matter whether it's true or not. It's not, we disagree with this program, we think we can do it better - it's, oh, this is a crisis!"

"So if you don't care about the facts, or the evidence, or civility, in general in making your arguments, you will end up with candidates who will say just about anything and do just about anything. And when your answer to every proposal that I make, or Democrats make is no, it means that you've got to become more and more unreasonable because that's the only way you can say no to some pretty reasonable stuff. And then you shouldn't be surprised when your party ultimately has no ideas to offer at all."

Despite his strong critique of the GOP, though, Obama added a caveat: