Early national polling is supporting the prevailing view in Washington that Democrats are in trouble in the 2014 midterm elections. While Democrats are more popular than the GOP among the general public, the party faces a number of challenges in November.

First, there's an enthusiasm gap. Typically, but not always, Republicans vote at higher rates than Democrats in congressional elections. And at this early stage, that seems likely to happen again, perhaps at an even greater rate than usual. One telling indicator came in December,...