The Republican Plan B is to repeal Obamacare on Day 1 of a Romney presidency.

Good luck with that.

First, today's Supreme Court decision will make it a lot harder to elect Mitt Romney. President Obama has just been handed a fearsome election weapon. 2012 is no longer exclusively a referendum on the president's economic management. 2012 is now also a referendum on Mitt Romney's healthcare plans. The president can now plausibly say that a vote for the Republicans is a vote to raise prescription drug costs on senior citizens and to empower insurance companies to deny coverage to children for pre-existing conditions. Those charges will hurt—and maybe hurt enough to sway the election.

Second, even if Republicans do win the White House and Senate in 2012, how much appetite will they then have for that 1-page repeal bill? Suddenly it will be their town halls filled with outraged senior citizens whose benefits are threatened; their incumbencies that will be threatened. Already we are hearing that some Republicans wish to retain the more popular elements of the Affordable Care Act (ACA). Which means the proposed 1-page bill will begin to grow.

Third, Mitt Romney has promised to grant states waivers from the obligations of the ACA. Not all states will ask for such waivers. Many will eagerly institute the ACA, which (let us not forget) includes large immediate grants of federal aid.

Fourth, Republicans will find the task of writing their "replace" law even more agonizing than the Democrats found original passage. The party has no internal consensus on what a replacement would look like. Worse, any replacement of the law's popular elements will require financing. But where is that money to come from? New taxes are unacceptable. The proceeds of "closing loopholes" are already spoken for—that's how President Romney has promised to finance his promise to cut the top rate of tax 28%. And he's also promised to increase defense spending.

Fifth, the clock is ticking. President Obama passed the ACA in the second year of his administration. A President Romney will have to pass repeal in the first year of his, because the law goes into effect in 2014. By then, states will have to have their exchanges up and working. And states that have put themselves through that work will not be very eager to see Washington undo it. If replacement does not happen in the first 100 days, it won't happen at all—that is, it won't happen as a single measure, but rather will take the form of dozens of small incremental changes adopted episodically over the next 20 years.

The outlook then: Even if Republicans win big in 2012, they will have to fight inch by bloody inch for changes they could have had for the asking in 2010. Truly, this is Waterloo—a Waterloo brought about by a dangerous combination of ideological frenzy, poor risk calculation, and a self-annihilating indifference to the real work of government.