For Democrats willing to see what's before their eyes, the nightmare came into sharper focus over the last week. Another 1994 might be in the offing. Back then, the beginning of the end came on a procedural vote. A Democratic majority that had held the House for four decades lost a routine party-line vote on a "rule," a basic measure allowing it to control the House floor. The August vote hit like a neutron bomb. Superficially, nothing changed: The Democrats still had a majority; they quickly re-established control and passed the underlying legislation, a liberal crime bill. Yet Republicans exulted...