I won't comment on the legal merits of the case because a) I'm not a lawyer, and b) I don't think the case will be settled on the merits anyway. The case will be seen by the court system as i) a partisan conflict, and ii) an attempt to overturn an election. Trump will win. Period.
So, let's perform a task we call "backwards induction," from game theory. What happens when Trump wins the case. Fill in the blanks for how he talks/tweets about the legal victory. It legitimizes the 2016 election.
Why do that? Given the Democrats' inevitable loss, the only thing they have to gain is if they think they can move public opinion with some revelation during the case, but public opinion of Trump, while perhaps not genius, has been stable. Remarkably so. Gallup has had him right around 40% as almost a fixed point. Donald Trump's 40% approval rating is our northern star of American politics. Opinions of him are fixed.
I... just don't see the point here. The 2018 midterm elections are right around the corner, and then there's 2020. Midterm elections run against the party of the president. The question is, by how much? Potentially by enough to swing one or both chambers. Right now, betting at PredictIt gives the Democrats an edge for the House, and Republicans an edge for the Senate. Why the difference? It's a matter of which seats are up this year. I'll write more about that later this year as we see the landscapes shape up. How susceptible are these probabilities to party strategy? Beyond candidate recruitment? That's... really hard to say, but that's where the DNC's efforts should be.
2020? Statistically, most incumbent presidents are reelected. Carter lost amid serious economic problems. George H.W. Bush lost amid public misperceptions of economic problems (the recession was long over, but people are... not very bright), but mostly, the GOP had won three presidential elections in a row, and it was, as Alan Abramowitz says, "time for a change." Johnson? Complicated. Basically, incumbents tend to win unless something weird is happening, but weird things happen. Trump won't be facing the "time for a change" penalty. What kind of economic or international issues will there be? No clue. Beyond that, then, I default to the observation that incumbent presidents win more than they lose, and they only lose under special circumstances.
Translation: Democrats, if they were smart about this, wouldn't push this lawsuit. They'd focus on the House and Senate, and try to use majorities there to a) draw out more scandals with subpoena power, and b) stir up as much trouble as possible to pin the blame on Trump. The worse things get, the better that gets for Democrats. "Politics ain't beanbag."
This lawsuit, though? The legal merits are irrelevant. The Democrats will lose, and it will probably backfire, even though, c'mon. Trump's campaign did collude. "Politics ain't beanbag."