The Affordable Care Act — the single most significant bill of Obama's first term — is law. It's law that mostly won't go into effect until 2014, but it's law nevertheless. Mitt Romney's key campaign promise was that, on day one, he'd begin working to pass a new law that would repeal it. But Obama doesn't have to do anything to make health reform happen. He doesn't need 60 votes in the Senate. He doesn't need 218 votes in the House. It's already happening. Obama's reelection is all that was required to for the United States of America to join every other industrialized country in having a universal — or at least very near-to-universal — health-care system.
The Dodd-Frank financial reforms are law. Again, Mitt Romney's promise was to pass a new law that would repeal it. If Obama is reelected, however, he doesn't need to ask Congress to work with him on Wall Street reform. They already did. Rather, the new regulations will continue to be hammered out and implemented. Wall Street will simply need to learn to live with them.
Tax increases are law. The Bush tax cuts are expiring at the end of the year, as is the AMT patch, as is the payroll tax cut, as are a host of smaller business tax cuts and stimulus tax cuts. Mitt Romney's promise was that he'd pass a law making sure taxes didn't go up (though he left open the possibility of permitting the stimulus cuts to expire). Obama's promise is that he won't sign a law that extends all the tax cuts. And if he holds to that promise, then taxes are going up, either through a negotiated compromise or simply letting current law take effect.
On their own, passing and implementing any of these laws would be a huge achievement for a presidency. The three of them together are a record and pace of domestic change unmatched by any recent administration. But they were an odd sort of change: Change that wouldn't happen until — and arguably unless — Obama secured a second term. Tonight, he did that.
They say that presidents campaign in poetry and govern in prose. That's rarely been truer for a president than it was for Obama, whose inspiring oratory launched him to the White House and whose grind-it-out, insider-game approach to working with Congress disappointed his fans. But it worked. That prose became law — but, unusually, it became law that wouldn't fully take effect until his second term. So while in 2008, his election was a vote for hope, in 2012, his reelection carries a guarantee of change.