The Democratic base is significantly less engaged and motivated to vote this year compared with the Republican base. Across several indicators of voter involvement Republicans have a double digit edge while Democratic engagement is remarkably low. From Gallup:
The only small upside for Democrats is that the enthusiasm gap isn’t quite as bad as 2010, but given that 2010 was a historic wave election for Republicans that is not saying much. Things are shaping up to be merely bad instead of historically bad.