In the past month, the GOP has gone from 44 to 48 on the generic ballot. That is a material change. For reference, they were at 48% at this point in 2010 and 46% in 2014. My gut tells me things are worse than advertised for democrats, although it is not showing up in the head-to-head polling yet. We know the midwestern polling has favored dems in the past few cycles ... so we might see a few surprises up there, unless the methodology has been improved.