The mid-term elections a little more than one year away (!). Control of Congress is often indirectly correlated with the President’s popularity.
Said differently, the factors that impact and/or determine the President’s popularity, often directly impact and or determine who controls the House of Representatives.
From Torsten Sløk:
The chart below shows the historical relationship between the President’s approval rating and the number of seats won or lost by the President’s party in the House of Representatives in midterm elections. Given the Democrats need to win 24 seats in 2018 to gain majority in the House the historical relationship suggests that President Trump needs an approval rating of at least 53% for the Republicans to keep a majority in the House.
The caveat is this has been such an unusual cycle, who knows if past correlations will hold up.