It's clear that Democrats are less enthusiastic about voting this year than Republicans. The latest evidence is from Gallup, which reports that the GOP's 3 percent edge in congressional voting among registered voters rises to 13 and 18 points when you include just those likely and very likely to vote. So why are Democrats less enthusiastic? And why has "the progressive donor base," as Democratic consultant Jim Jordans reports, "stopped writing checks"? It's not just because the economy remains sour or that President Obama failed to jam a public option in the health-care bill. I find a more convincing explanation...