When last seen before election day 2006, the Democratic Party seemed the very soul of moderation. And they stayed the course for the next two months. House Democrats refused to replace their No. 2, the moderate Steny Hoyer, with the antiwar Jack Murtha. Speaker Nancy Pelosi emphasized her maternal and grandmaternal qualities as she shepherded through the House a modest and popular agenda of ethics reform, a minimum-wage hike and cheaper drugs for seniors. The Democratic presidential flavor of the month in the shopping season before Christmas was the fresh-faced, not-too-partisan Barack Obama.
But in the past few weeks, the Democrats...