When the Democratic base voters and activists are enthusiastic about an election Democrats usually win that election.
In the 2008 election about 80% of the Democratic base was very enthusiastic about the election. Obama and Democratic congressional candidates won big at the polls that year.
In contrast, the Democratic base, disappointed by the failure of elected Democrats to stand up to Republican and defend progressive values as strongly as Republicans defend conservative values, polled an enthusiasm level of only 60 percent. The 2010 enthusiasm gap between Democrats and Republicans allowed Teapublican candidates to win control of the U.S. House, as well as many state legislatures and governors' mansions.
According to the new Gallup poll, the gap between the Democrats’ level of enthusiasm compared to the Republicans’ level of enthusiasm is the largest it has been in a decade. A large enthusiasm gap is a bad thing in any political environment, but it’s especially problematic for the Obama campaign, which depended on high enthusiasm to get large turnout numbers from infrequent voters groups, such as young adults in 2008.
After the 2010 Democratic wipeout there was some hope among Democrats that the 2012 Congressional elections wouldn’t be as bad because having Obama on the ballot would inspire his 2008 surge voters to come out again. At this point though, it looks as if Obama’s ability to increase base enthusiasm or turnout is limited.