Democrats are suffering from a dangerous enthusiasm gap. On the generic ballot, Democrats are currently tied with Republicans for the 2010 midterm election at 44 percent each, according to the new NBC/WSJ poll. That’s bad news for Democrats, given that they are holding several Republican-leaning seats and suffer a built-in disadvantage based on the layout of Congressional districts.

What is truly onerous for Democrats is that Republicans are much more enthusiastic about voting. From MSNBC:

Republicans also enjoy a significant advantage among those most enthusiastic about the midterms — they prefer the GOP controlling Congress by 20 points.

Midterm elections are all about turnout, and that’s a huge gap. If Republicans are significantly more fired up, that swings a lot of seats to the GOP column. Traditional Democratic voters are simply not overjoyed with the results of having put the Democrats in complete control of Washington, and are not enthusiastic about helping them stay in power.

Just in case Democrats have no idea why their base is tepid, I can provide some help: It starts with 10 percent unemployment and a mountain of unmet promises.

The LGBT community did not get “don’t ask, don’t tell” repealed, despite a promise embedded in the State of the Union speech. Obama is now running from immigration reform, which he promised to Hispanics this year. Labor never got and probably never will get the Employee Free Choice Act. Environmentalists are faced with an awful climate change bill. Pro-choice voters got kicked in the teeth with the health care bill, and after months of dancing around the issue, Obama quietly killed the public option.

How to close the enthusiasm gap? Give voters something to be enthusiastic about. I don’t see any legislation aspiring to do that, especially with House Democrats cowering in fear instead of governing. Unless we see a serious improvement in the economy, or a meltdown by the Republicans, this enthusiasm gap could be very costly for Democrats.