Will the democrats win in 2018? It’s a question worth asking. There are a number of reasons to think that they will.
First off, the party of the president almost always loses seats in midterm elections. The only exception to this in the 21st century was the 2002 elections.
Second, there is definitely a gap in partisan motivation. Elections are not won by majorities, but by who shows up to the polls. Motivation, therefore, is particularly important in midterm elections, which have lower turnout than presidential races.
Why are democrats more motivated? Brett Kavanaugh’s confirmation, for one, is likely to intensify anger on the left for quite a while. Donald Trump’s regular shredding of American norms is not helping his party either.
Furthermore, the GOP has struggled to craft a message for the midterms. Democrats, at least, can run on healthcare and opposition to Trump. What can the GOP run on?
All signs do point to a democratic wave in November. The question, then, will be whether it’s enough to flip the House and Senate.
That will be decided by turnout on a state level, and also by the extent to which democrats can overcome gerrymandered districts in red states.
After 2010, the GOP engaged in a campaign to redraw House district maps to their advantage, and were largely successful in doing so. Some of these maps have been struck down by the courts, others have stayed in place.
Without gerrymandering, it’s pretty likely that the democrats would take the House by a comfortable margin.
In the final analysis, I’d say that the Senate is a toss-up, and the House is likely to go to the democrats.