It looks like Democrats are going to get approximately +7 percentage points in the popular vote totals. This will meet or exceed what the GOP got in 2010 with the Tea Party wave. It won't translate into the same number of seats due to gerrymandering, but it's still a small victory. The Affordable Care Act appears to be safe for now.
Having House Democrats trying to litigate the Russia investigation is problematic even if they produce some bombshells, because no matter what they release to the public, it will be viewed through the prism of politics. What I had hoped is for a serious body blow that would have forced Republicans in the House, the Senate, and the Legislatures to stop and say "Whoa, maybe it's time to think of getting off the corruption car on the Trump train." Not that I expected it, but the sobering reality is that it just didn't happen. So yes, the Dems can call for witnesses and tax returns, but it's not going to have the same impact.
I think the Democrats are going to have to wait for Republicans to make political mistakes and capitalize when they do. One of the first and most serious mistakes could be the lawsuit against Obamacare. Dems ought to be ready to pounce on that and make it an issue. That's going to cause millions to lose health care coverage, and it's going to piss voters off and more importantly, expose one of the most blatant lies that people somehow bought in this past election: that Republicans actually care about the issue of healthcare coverage. If they miss the opportunity to capitalize on that, because they're focused on trying to litigate the Russia investigation, that'll be one hell of a missed opportunity.