It hasn't mattered if the President's party is Republican or Democrat, the President's part has almost always lost seats in the House no matter what the job-market has done. The only time the Republicans gained seats was after 9/11.
What has mattered more is Presidential approval. The more unpopular the President, the more likely the President's party lost seats.
Job-Market Boost in the Midterms? Evidence Suggests No
Of course, the partisans will be like "It doesn't matter this time. My party is awesome and your party sucks. We're going to win seats because I really, really, really want my party to win. Blah, blah, blah." It's always like this every two years.
What has mattered more is Presidential approval. The more unpopular the President, the more likely the President's party lost seats.
Job-Market Boost in the Midterms? Evidence Suggests No
Of course, the partisans will be like "It doesn't matter this time. My party is awesome and your party sucks. We're going to win seats because I really, really, really want my party to win. Blah, blah, blah." It's always like this every two years.