Well, if they're going to do so, they'll have to do show a lot better for Team Red than they're currently doing in the polls. Two just-released polls from Quinnipiac and CNN report predictable advantages for the Democrats in the generic Congressional ballot among minority voters and white college graduates but just 13 and 10 point advantages, respectively, among white noncollege voters for the Republicans. That is far below levels of support the GOP likely needs from their base voter group to stave off the Democrats in November.
By comparison, the exit polls indicated a 30 point advantage for the Republicans among white noncollege voters in 2014 and well over 30 points in 2016 (other estimates more reliable than the exit polls also had the GOP white noncollege advantage over 30 points).
So, yes this is national data and the races are not national this year. But this is a very bad sign for the Trumpified GOP. Could the bloom be off the rose, so to speak among the white working class? Keep your eye on this one in November.