Despite this, some on the right are gloating that Obama had been maneuvered into forfeiting his liberal base. Nonsense. He will never lose his base. Where do they go? Liberals will never have a president as ideologically kindred - and they know it. For the left, Obama is as good as it gets in a country that is barely 20 percent liberal.
It's possible that Krauthammer is being intentionally forgetful here, but a few liberals -- not a lot, but enough to make a difference -- cast their votes for Ralph Nader in 2000. Not because they thought he'd be president, but because they didn't think it mattered if a Democrat or Republican held office. The presidency of George W. Bush heightened the contradictions between the two major parties in ways that have given plenty of former Naderites pause since then, but there are plenty of liberals whose disgust with a centrist Democrat might cause them to A) abandon politics altogether for a cycle or two, or B) find the new Nader, or a lefty equivalent of Ron Paul. (Dennis Kucinich, I'm NOT looking at you.) The idea wouldn't be to win the presidency right away, but to begin building a serious, viable third party that could offer voters an alternative. I'm not saying it would be successful, but there *is* someplace for liberal voters to go.