Another liberal crack-up

For the fourth time since the 1960s, American voters in 2008 gave Democrats overwhelming control of both Congress and the White House. Republicans haven’t had such large majorities since the 1920s. Yet once again, Democratic leaders have tried to govern the country from the left, only to find that their policies have hit a wall of practical and popular resistance.

Democrats failed in the latter half of the 1960s, as the twin burdens of the Great Society and Vietnam ended the Kennedy boom and split their party. They failed again after Watergate, as Congress dragged Jimmy Carter to the left and liberals had no answer for stagflation. They failed a third time in the first two Bill Clinton years, as tax increases and HillaryCare led to the Gingrich Congress before Mr. Clinton salvaged his Presidency by tacking to the center.

A fourth crackup is already well underway and is even more remarkable considering how Democrats were set up for success. Inheriting a recession amid GOP failures, Democrats had the chance to restore economic confidence and fix the financial system with modest reforms that would let them take credit for the inevitable recovery. Yet only 13 months later, Democrats are down in the polls, their agenda is stymied by Democratic opposition, and their House and Senate majorities are in peril as moderates like Mr. Bayh flee the scene of this political accident.