President Obama today accused Republicans of political extortion, saying they are trying to "blackmail a president" by threatening to shut down the government or refuse to raise the debt ceiling unless he agrees to gut his signature health care law.

Making a sales pitch for "Obamacare" before a crowd of students in Maryland, the president said that critics of the Affordable Care Act have become "more irresponsible" as implementation approaches.

"Some have threatened a government shutdown if they can't shut down this law.

Jacquelyn Martin/AP Photo

Others have actually threatened an economic shutdown by refusing to pay America's bills if they can't delay the law. That's not going to happen as long as long as I'm president," he said to cheers at Prince George's Community College. "The Affordable Care Act is here to stay."

Three-and-a-half years after the bill was signed into law, the president spent the bulk of his nearly hourlong speech detailing the benefits of Obamacare in an effort to encourage a skeptical American public to enroll starting on Oct. 1.

The president accused Republicans of "fearmongering" and mocked them for going to "crazy" extremes to try to block implementation.

"The Republican party has just spun itself up around this issue," he said. "The fact is, the Republicans' biggest fear at this point is not that Affordable Care Act will fail. What they're worried about is it's going to succeed."

As House Republicans try to attach proposals to defund or delay Obamacare to measures to fund the government or boost the nation's borrowing ability, the president made clear that he is not willing to negotiate over the debt ceiling. "This is the United States of America. We're not a deadbeat nation," he said. We don't run out on our tab."

"That's why I will not negotiate on anything when it comes to the full faith and credit of the United States of America. We're not going to submit to this kind of total irresponsibility," he continued.

The president did admit that there will be "some glitches along the way" in getting the new exchanges up and running. "Every law has hiccups when it's first starting off," he said.

"Once it's working really well, I guarantee you they will not call it 'Obamacare,'" he joked of his critics.

"A few years from now, when people are using this to get coverage and everybody's feeling pretty good about all the choices and competition that they've got, there are going to be a whole bunch of folks who say, Yeah, yeah, no, I always thought this provision was excellent," he said to laughter. "I voted for that thing. You watch."