FiveThirtyEight puts a Democratic majority in the House at an 83% chance with a median of a 36-seat gain.
They don’t take Russian interference into account at all, otherwise I’d be pretty close to agreeing.
I don’t see how Russian interference could be so widespread as to send dozens of individual seats all over the country into Republican control.
It seems like a smaller job than 2016 to me. They’d just need to target specific close congressional races, which is exactly what they already did in 2016 (the less-reported Russia story is it wasn’t just Trump they assisted, but dozens of downballot Republican Congressional candidates as well). So they just repeat 2016 without having to worry about the President this time. The overall national vote tally could be more-or-less unchanged, most districts could swing hard toward the Democrats, but close races could simply defy the national average and not swing enough. And the Russians have a freer hand to do things this time, with no federal coordination of cybersecurity anymore, more well-positioned Russian assets in government this time, etc. And maybe they don’t just play with Facebook and stealing e-mails anymore, but start corrupting voter databases to make voters in key districts ineligible (why bother changing votes when you can just make specific votes not count, right Mr. Kobach?). No need to assume they’d use the same tactics twice, although I think it’s pretty safe to assume they’d have the same objective.
Will any of this happen? Who knows? I’m saying it’s a risk that’s plausible enough to consider and take into account for predictions, since it already happened once before and the conditions are actually more favorable for them this time around. It’s also quite plausible that 2016 was a one-off and that the general public now has the benefit of knowing well in advance that the Russians plan to attempt to swing the election in favor of the Republicans (although, to be frank, everyone with an ounce of sense knew that going into 2016 as well) – it’s one of our “known unknowns” in Rumsfeld-speak.