The Supreme Court decision upholding the Affordable Care Act is big — but it’s hardly the end of the story. So what’s next?

The biggest and most obvious remaining hurdle for the ACA is that if Mitt Romney wins and Republicans wind up with unified control of Congress, there’s every possibility that the law could still be entirely repealed.

But even if that doesn’t happen: what remains is a lot of trench warfare. The Court supplied the states with even more room to fight against reform than they already had (increasing their options on the Medicaid expansion portion of the law). Insurance companies and other interest groups can appeal to regulators in the executive branch or to Congress to defeat specific provisions they don’t like — and that hasn’t changed today. Those two things could, together, wind up undermining the law, especially under a President Romney, even if the votes aren’t there for full repeal.

Still, Obamacare lives, and it’s going to be harder and harder to repeal as time goes on. That’s obviously good news for those who are particularly helped by the law: those of us who don’t work for big companies that provide good insurance and don’t qualify for Medicare.

As for the politics: What’s really important here is that it underscores just how important this presidential election will be. The radicalism of the four dissenters is a harbinger of what could happen. Four — or eight — years of Mitt Romney would almost certainly cement a very conservative majority on the Supreme Court, willing to make radical changes in the way the United States government has operated since the New Deal. On the other hand…four more years of Barack Obama’s presidency could well preserve the status quo for a long time: a conservative Court, but one which is not quite able to upend the rest of the political system.

Which means that for those who walked precincts, worked phone banks, and otherwise worked to elect Barack Obama because they wanted to reform health care, today’s decision is a reward — and an admonision. It’s time to do all that stuff again. Democracies only create temporary victories, which have to be repeated to be sustained. And in this particular democracy, that means not just in presidential elections, but in Congress too — and, as the Medicaid portion of the decision reminds us, it means gubernatorial and even state legislative elections as well.

And that’s as it should be. Opponents of health care reform are hollering about “liberty,” but real liberty doesn’t reside in any particular policy outcome, but in the fact that we continue to fight over those outcomes. This whole battle is a reminder of how d ifficult it is for even the winners to get anything done — and to keep it in place. So we’ll all fight it out again in the 2012 elections…and the 2014 elections, and the 2016 elections. The real message from the Supreme Court to all those who support and all those who oppose the Patient Protection and Afforadable Care Act? It’s an election year: get to work.

For more on the Supreme Court ruling:

Greg Sargent: Landmark decision marks new era for federal power

Erik Wemple: CNN blows its first reaction to the health-care ruling

Jennifer Rubin: Turning the political and legal world upside down

Stephen Stromberg: Court saves U.S. from policy pileup

Ed Rogers: Obama won ugly, and only temporarily

Carter Eskew: Supreme Court decision gives new life to President Obama

Kathleen Parker: Winning the day with deceit