Dem
51
GOP
49
The House is much more tied to national waves than the Senate because far more people know who their senators are than who their representative is. With the Senate, the candidate quality often matters. With the House, it's all about the (D) or (R). Consequently, Republican insiders think that their control of the House stands or falls with Donald Trump's success at the ballot box.
Republicans are confident about winning back the Senate because they have to win only one contested Senate race to get control. The most plausible way for the Democrats to retain control is for them to win every one of at least half a dozen contested races and also the vice presidency. It's not impossible, but it might take a blue wave to pull off. The House is completely different because there are dozens of contested races and winning a simple majority is enough. You don't have to win them all. For this reason, the Democrats are more confident about the House.
According to the Cook Political Report, 210 seats lean Republican or better and 203 lean Democratic or better. Twenty-two seats are true tossups, and each party controls half of them now. Gerrymandering in North Carolina will change the delegation from 7D, 7R to 4D, 10R. New York Democrats could have gone for the jugular but refrained from doing so. A couple of new maps in the deep South could help the Democrats though.
Sen. Thom Tillis (R-NC) thinks that if Trump performs well in the swing districts, his coattails will do the job for House Republicans; otherwise, no.
Of course, there are other factors, such as the GOP's infighting and its inability to govern, even with a House majority. With a similar majority, Rep. Nancy Pelosi (D-CA) was able to pass bill after bill due to her leadership. Democrats also have a fundraising advantage. Still, Trump could play an oversize role, both due to his own performance and whom he endorses. (V)