Dems at this point in 2006 were dominating the generic ballot polls. Now, its shrunk.
2018 Generic Congressional Vote
2014 Midterm Polls | 2010 Midterm Polls | 2006 Midterm Polls | 2002 Midterm Polls
Economist/YouGov 5/27 - 5/29 1279 RV 42 39 Democrats +3
Rasmussen Reports 5/21 - 5/25 2500 LV 43 42 Democrats +1
Harvard-Harris 5/21 - 5/22 1347 RV 44 37 Democrats +7
Reuters/Ipsos 5/18 - 5/22 1080 RV 40 37 Democrats +3
CNN 5/2 - 5/5 901 RV 47 44 Democrats +3
Pew Research 4/25 - 5/1 1221 RV 48 43 Democrats +5