My biggest fear of an Obama Presidency is not what he might do but what a Democratic Congress with an expanded majority might do. I fear the Senator Obama will not be able to resist the worst urges of Democrats who believe they have been given a mandate to enact every liberal pipe dream from a carbon tax to nationalized health care.

Michael Gerson has similar worries:

Following an electoral victory, Obama is likely to face a massive challenge: The least responsible, least respected, least popular political institution in America — the Democratic-led Congress — would also be the most emboldened. Democratic leaders with large majorities would be pushed by conviction and hubris, and pressured by Democratic constituencies, toward divisive measures that punish and alienate businesses, seek backward-looking political vengeance and impose cultural liberalism. This predictable story of overreach, backlash and bitterness easily could destroy Obama’s presidency, even before his first achievements — unless he can suddenly find the ability to shape, tame, even fight, the self-destructive tendencies of his own party.

I don’t expect that Obama will have the stomach to fight his own party. He’s certainly shown no indication of it so far.