Well, one could make a long list of laws that were controversial when passed and opposition to which increased after their passage: the Alien and Sedition Acts, the Fugitive Slave Law and the Kansas-Nebraska Act come to mind. But the big example from modern times would seem to me to be Prohibition.
National Prohibition was the desire of a strong movement that had been around for a long time. Years and years of agitation finally yielded, not a single Act, but a Constitutional Amendment! And yet, no sooner had the Great Experiment begun that it began to show its flaws. People -- whole communities -- widely ignored it. There were all kinds of gimmicks for getting around it. Congress didn't fund its enforcement. Crime exploded, especially gang-related crime. Our borders and coasts became battle zones. It was a disaster. Repeal took a dozen years and another Amendment.
Those who oppose Obamacare want to fix what's wrong in our health care system. They just realize that this turkey won't do that; indeed, Obamacare is going to make things worse, far worse than before. The Obamacare system is corrupt, the cost astronomical, the benefits patchy, the impact upon jobs awful. The opponents are not radicals, not anarchists, not obstructionists. They are trying to fix what's wrong in the face of a united movement determined to foist this thing on the nation.
There are other ways to fix what's wrong with our health care system. Many good ideas to do just that were offered when this Act was debated. The Democrats in Congress would not allow a single one of the Republican amendments to be considered. They own this thing, lock, stock, and barrel. Which is why they are fighting so hard to keep it now, even though they know how awful it is; if they didn't fight for it, they'd have to admit they deliberately misled the American people when they passed it. The real obstructionists in this debate are people like Harry Reid, Nancy Pelosi and Chuck Shumer.
It took twelve years to get rid of Prohibition. Some of the social costs, like organized crime, are still with us. I don't know how long it will take to get rid of Obamacare, or how long it will take our economy to recover from it, but the job's got to be done.