(Image Credit: Mark Wilson/Pool via Bloomberg /Getty Images)

Asked if he was preparing for the Supreme Court to overturn his signature legislative achievement, the health care law passed in 2010, President Obama said today he was confident the law's constitutionality would be upheld - but he seemed to suggest he was preparing arguments to make should that not be the case.

"Ultimately, I'm confident that the Supreme Court will not take what would be an unprecedented extraordinary step of overturning a law that was passed by a strong majority of a democratically elected Congress," the president said.

How "strong" a "majority of a democratically elected Congress" is disputable. The bill initially passed 60-39 in the Senate - that's a strong majority, but it's also the minimum needed to pass anything in the Senate these days, given the constant filibuster threat. The vote was a narrow 220 to 215 in the House, just two votes more than the 218 needed. The second time it came through the House it passed 219-212.)

He said he would "just remind conservative commentators that for years what we've heard is the biggest problem on the bench was judicial activism or a lack of judicial restraint, that an unelected group of people would somehow overturn a duly constituted and - and passed law. Well, there's a good example, and I'm pretty confident that this court will recognize that and not take that step."

At another point, the president misspoke, almost saying he was sure the law would be overturned. "We are confident that this will be over, that - that this will be upheld," he said, correcting himself.

The president also said that "this is not an abstract argument. People's lives are affected by the lack of availability of health care, the inaffordablity of health care, their inability to get health care because of pre-existing conditions."

He said the law has "already given 2.5 million young people health care that wouldn't otherwise have it. There are tens of thousands of adults with pre-existing conditions who have health care right now because of this law. Parents don't have to worry about their children not being able to get health care because they can't be prevented from getting health care as a consequence of a pre-existing condition. … Millions of seniors are paying less for prescription drugs because of this law. Americans all across the country have greater rights and protections with respect to their insurance companies and are getting preventive care because of this law."

And, he underlined, "that's just the part that's already been implemented. That doesn't even speak to the 30 million people who stand to gain coverage once it's fully implemented in 2014."

He said he thinks "the American people understand, and I think the justices should understand, that in the absence of an individual mandate, you cannot have a mechanism to ensure that people with pre-existing conditions can actually get health care. So - so there's - there's not only a(n) economic element to this and a legal element to this, but there's a human element to this. And I hope that's not forgotten in this political debate."

While the president remained relatively cautious in his comments, he has criticized the Supreme Court before - most publicly in his 2010 State of the Union address, when he took on the decision in the Citizens United case, saying "with all due deference to separation of powers, last week the Supreme Court reversed a century of law to open the floodgates for special interests - including foreign corporations - to spend without limit in our elections."

Justice Samuel Alito could be seen mouthing the words "that's not true," with which many historians agreed.

Last November, the president said of this court case, "if the Supreme Court follows existing precedent, existing law, it should be upheld without a problem. If the Supreme Court does not follow existing law and precedent, then we'll have to manage that when it happens."

The president made his remarks today at an event in the Rose Garden with Mexican President Felipe Calderon and Canadian Prime Minister Stephen Harper.

On March 27, ABC News asked White House press secretary Jay Carney the following: "The President has made it very clear with his address to Congress a few years ago that he disagrees with some of the decisions that have been made by this court and, I think it's fair to say, questions their thinking. Is he not concerned about this case going before this court?"

Carney responded: "Well, he and his advisers believe that the constitutionality of the Affordable Care Act is established and we're confident that it will be upheld by the Supreme Court based on that. There's no question that the president believes very strongly that the Citizens United decision was not a good one, that it's had the kind of negative effects on the American campaign system, political system, that he anticipated and feared, and that we're now seeing vividly in this campaign cycle… We'll see how the court decides. "

- Jake Tapper and Mary Bruce