DISCUSSING the troubled implementation of Obamacare, Ezra Klein remarks that "no big law ever fully survives first contact with reality". A friend of mine, a political theorist, once had a related thought. Political ideologies purified of concerns about real-world feasibility are like hunks of cheese, he said, and the reality of human political and social life is like a cheese grater. Each glorious golden hunk of ideological cheddar or Gruyère is left in shreds upon contact with the world. The gist of his idea is correct, but the formulation is overly optimistic. Shredded cheddar tastes like cheddar. Shredded politics tastes like... You know what it tastes like. Not like Gruyère. Mr Klein observes that congressional Republicans, unable to repeal Obamacare outright,

also refuse to permit any tweaks or technical correction that would help it work better. In fact, they’re creating new problems by withholding implementation funds. This is a real problem for the law, and for the country. Back in January 2011, I called it the biggest danger for health reform, and I still think that’s right: If it persists, “what America will get is not the Affordable Care Act, and nor will it be repeal of the Affordable Care Act. It’ll be a hobbled version of the Affordable Care Act, where what works isn’t expanded and what fails isn’t replaced. And though that might be better than nothing for the uninsured, it will be pretty terrible policy.”

Mr Klein characterises the situation as one in which the GOP is pursuing a "dangerous", "heighten-the-contradictions strategy" of strafing Obamacare while it totters on fawn's legs, gambling on the chance that this will help them seize the Senate and scotch the law altogether. This is, perhaps, half the story. We might further characterise the situation as follows. Democrats knew Obamacare was rabidly opposed by Republican voters across the country, and knew it would be shredded in implementation, but were willing to settle for what they knew would turn out to be "pretty terrible policy" as long as that was "better than nothing for the uninsured". After all, they'd be able to take credit for the expansion in coverage and, with the help of sympathetic journalists, blame all problems, expected and not, on Republican obstructionism. And here we have Mr Klein, right on cue, tsk-ing Republicans for playing politics, of all things, with the health and welfare of Americans.

Once, when I lived in Washington, DC, I parked my bike against the stoop of my house and popped inside to grab my wallet. When I came out again, about three minutes later, my bike was gone. I called the police, and they came. They asked if I had locked it up and I admitted that I hadn't, that I had only run in for few minutes. They laughed. They laughed in my face. What did I expect would happen with an unlocked bike?!

One might ask a similar question to Mr Obama. What did he expect would happen if he signed a cumbersome, dubiously constitutional, hotly contested, not-very-popular piece of delayed-action legislation which barely squeezed through an unprecedentedly polarised congress?

The difference between the theft of my bike and the GOP's attempted piecemeal dismantling of Obamacare is that theft is a crime, while an opposition party's strategic resistance to the implementation of a law reviled by the party's supporters is practically an obligation. In any case, it's predictable. The Republican cheese grater announced in the clearest possible terms a resolute intention to run Obamacare through a thousand tiny blades, and has kept its word. The Democrats gambled, are still gambling, that the pile of predictably-grated health-care policy won't in the end taste like dust in American mouths.

All that said, I don't wish to credit Democrats with too much foresight. Liberals were dismissive of the constitutional challenge to the individual mandate right up until Don Verrilli lost his eyebrows to a scorching line of questions from the conservative majority on the Supreme Court. If John Roberts had eaten a bad buffalo wing at a crucial moment, Obamacare might have been doomed, and Democrats wouldn't have seen it coming until far too late.

Similarly, I don't think Mr Obama predicted that so many states would refuse, as mine has, to set up health-plan exchanges. As Ramesh Ponnuru notes, "most states have refused to establish the online marketplaces, and both the tax credits and many of the law’s penalties can’t go into effect until the states act". What then? "Obama’s IRS has decided it’s going to apply the tax credits and penalties in states that refuse, even without statutory authorization." And this may lead to legal challenges probably not anticipated by the White House. Does this imperfect foresight mean that if "pretty terrible policy" emerges from Obamacare's contact with hostile political reality, Democrats are off the hook for at least the terribleness they honestly failed to anticipate? I don't know. I remain convinced that it was reasonable to believe my bike would still be there.

This raises an interesting, tangentially related question. Liberals fulminate constantly against outrageous conservative obstruction, yet often seem nevertheless surprised by its effectiveness. Why is that? My guess is that liberals are sometimes deceived by assumptions about the scope of liberalising moral progress. Modern history is a series of conservative disappointments, and the trend of social change does have a generally liberal cast. The surprisingly rapid acceptance of legal gay marriage is a good example. Liberals are therefore accustomed to a giddy sense of riding at the vanguard of history, routed reactionaries choking in their dust. But all of us, whatever our colours, overestimate the moral and intellectual coherence of our political convictions. We're inclined to see meaningful internal connections between our opinions—between our views on abortion and regulatory policy, say—when often there's no connection deeper than the contingent expediencies of coalition politics. For liberals, this sometimes plays out as a tendency to see resistance to all liberal policy as an inevitably losing battle against the inexorable tide of history. This occasionally leads, in turn, to a slightly naive sense of surprise when a hard-won political victory isn't consolidated by a decisive, validating shift in public opinion, but instead begins to be ratcheted back.