These charts were made using numbers in the newest Economist / YouGov Poll -- done between December 31st and January 2nd of a random national sample of 1,500 adults (including 1,277 registered voters), with a 3 point margin of error.
Will 2018 be a wave election -- flipping control of Congress. It's possible. Congress is certainly unpopular enough (and Trump has no coattails to offer his fellow Republicans. Only 14% of the public thinks Congress is doing a good job. And nearly half of the public blames the Republicans (48%) for that, while only 12% blame the Democrats.
The Democrats have a 7 point higher favorable rating than the Republicans do, and in the generic vote they lead by 6 points. The Democrats have a golden opportunity in 2018 -- if they can get their voters to the polls on election day.