When the president signed the bill that's become known as Obamacare more than two years ago, Democrats rejoiced. The expansion of health care was a landmark the party had tried–unsuccessfully–to enact for decades…and the president believed it would go down in history as his legacy:

"Today, after almost a century of change. Today, after over a year of debate, today after all the votes have been tallied…health reform becomes law in America,” the president said after signing the bill on March 23, 2010.

What the president did not say is that all the votes for the bill came from Democrats…not one from Republicans.

As the Democrats celebrated, the Republicans began the legal challenge the Supreme Court should resolve tomorrow.

The court has three choices: uphold the entire Patient Protection and Affordable Care Act; kill it all; or issue a split decision: ruling part of it unconstitutional.

And the part that may be ruled out is the heart of the law: the individual mandate, requiring all Americans to buy health insurance, whether or not they want to.

"We don't need to re-fight this battle over health care," President Obama said.

The president and most Democrats have always said the Supreme Court would never throw out the individual mandate. But now they're realizing it could happen tomorrow.

And so does Mitt Romney:

“If Obamacare is not deemed constitutional, then the first three and a half years of this president's term will have been wasted on something that has not helped the American people," Romney said.

A new NBC poll shows 41% of registered voters think the president's plan is a bad idea…while just 35% think it's a good idea.

So however the Supreme Court rules tomorrow, it's clear the White House misjudged how popular his plan would be:

"As people become familiar with it, it will sell itself," senior presidential adviser David Axelrod said 2 years ago.

To paraphrase the vice-president, this is a big deal.

The president's signature bill is at stake, and the Oval Office may be, too.

I hope you get a good's night sleep tonight….but I don't think the president or Mitt Romney will.

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