Listen closely to all those cheers for newly crowned nominee Barack Obama, and in the background you'll catch the notes of a funeral march. Resting, if not in peace, are the New Democrats.

The Illinois senator's primary victory marked the end of many things, and one looks to be his party's 20-year experiment with ideological centrism. The New Dems are still out there, still urging their party to fight its natural liberal instincts. But who's listening? Buoyed by the Republican implosion, wild for their retro nominee, the intellectual...