I remember reading, way back when Kennedy retired, that McConnell was threatening to confirm a Justice just before the midterm elections (if Democrats didn't accede to some demand of his that I've forgotten), with the logic that doing so would demoralize the Democratic base. This was before Kavanaugh, of course: the bases are certainly fired up, but there could be a significant difference in degree (i.e. complacency).
Five-Thirty Eight says Dems have a 2/9 chance of taking the Senate, and a 3/4 chance of taking the House. Last I looked at them, it was 1/3 Senate and 2/3 House, so there's been some slight movement, but not very consistently. RCP's averages put the likely Senate at 51-49, with each party gaining two seats.
Trump 100% certain that Ford named the wrong person in her accusation.
100%, even though he wasn't even there? I'd never say I was 100% certain of anything unless I was personally there, and perhaps not even then. But that's surely my fault for attempting to apply reason to Trump's pronouncements...
They don't exactly control the Supreme Court, heavily in favor, yes, but it depends on what the issue being ruled on is.
Consider that, given the Supreme Court as it now stands, they would
still likely rule in favor of Obamacare, with Chief Justice Roberts as the deciding factor.
Polls did drop closer... if not significantly, then noticably during the Kavanaugh fight. I think Dems actually hurt themselves with their political maneuvering during the whole thing. It was quite embarrassing. Combine that with the fact that Dems are feeling dejected and tired, the hope that they might flip the senate and stop Kavanaugh is gone. It probably wasn't the best time for the fight to happen. House is still somewhat safe to flip... but I think it'll be closer than anyone likes.
There's no such thing as general polls in midterms, though. The difference between the Senate and the House should be as good evidence as any of that. And I just don't see it having much effect. Democrats are outraged, Republicans are brushing it off in favor of "winning", moderates are unsettled and decry the degradation of norms. So essentially the same thing that's been happening for the last two years.