The good news for Democrats:  the enthusiasm gap among Republicans is the worst recorded.  The bad news:  Democrats are even less enthusiastic about voting in 2014.
Among registered voters, 42% of Republicans and Republican-leaning independents currently say they are more enthusiastic than usual about voting, while 50% are less enthusiastic, resulting in an eight-point enthusiasm deficit. But Democrats are even less enthusiastic, with a 23-point deficit (32% more enthusiastic vs. 55% less enthusiastic).

Typically, the party whose supporters have an advantage in enthusiasm has done better in midterm elections. Republicans had decided advantages in enthusiasm in 1994, 2002, and especially 2010 -- years in which they won control of the House of Representatives or expanded on their existing majority. Democrats had the advantage in 2006, the year they won control of the House. Neither party had a decided advantage in 1998, a year Democrats posted minimal gains in House seats.
At this point, neither party could give a damn, but the GOP still has a 15 point edge.  They had a 34 point edge in 2010 and the GOP picked up 60 plus seats in the House, where Democrats had a 13 point edge in 2006 and won the House there.

With all the gerrymandering and the power of incumbency, it's looking like there's not going to be too much of a shift in either the House or Senate.  That's at least something in the "Dems will keep the Senate out of inertia" column.

The thought and enthusiasm measures together suggest a mixed picture for Republicans. On one hand, it seems clear that 2014 will not be a repeat of 2010, when record Republican enthusiasm presaged major gains for the party in Congress. This year, Republicans' reported enthusiasm not only pales in comparison to 2010, but also to every other midterm election year.

However, Republicans still maintain advantages in thought given to the election and in voter enthusiasm compared with Democrats, and these advantages normally point to a better year for Republicans than Democrats. There is some uncertainty about how that will play out this year given that both Republicans and Democrats say they are less enthusiastic than usual about voting -- something that has occasionally occurred in past midterm election years but never over the course of an entire midterm campaign.
The danger of course remains that Democrats don't care what happens in 2014 and won't vote.  It just means there will be closer races that we could have won and didn't rather than 2010 style blowouts, but to see the Democratic numbers this bad (even in 2010 it was 44% a piece for enthusiastic versus non) it means that we're still going to lose.

Unless we vote.