I posted a New Yorker article a while back that, using statistics and history, suggested that the Republicans would lose seats in the 2018 mid-terms. Its still quite possible that it will happen, it is noteworthy however that so far in the 2017 special elections, the Republicans are 5-0 over the Democrats.
This even though the Democrats are spending money like crazy to try to get the narrative that Trump has imploded the party going. Trump's mouth (or fingers) are not helping but its quite possible that economic insatisfaction (from secular stagnation/new normal) means that the Republicans will get a chance for a while, they might the benefit of the doubt because people want a different agenda, if that's the case, they will have a higher chance of keeping seats (or even get more seats) in the 2018 mid-terms despite what statistics with small sample sizes say
I don't know what will happen there but I have to bring this up because the stupidity of the media in these matters is rampant. By reading articles you would think the Republicans got no chance, the agenda is dead and people need to bail out of stocks, yet if that's wrong (that is, the Republicans keep/expand seats and the agenda moves forward), the consequences are exponential to assets like stocks.
Therefore, one has to be VERY careful about joining the media perma view that the Republicans are done for. This is not a situation where an edge is achieved by being right 51%+ of the time, you have to be right a lot more often than that because of the exponential component of the stock market payoff (that plays out through either a huge year or two or by an extra few percent in returns over long periods of time).