One great election day does not a revived party make, but Democrats have to be feeling pretty darn good right now. And there's one man they have to thank for the reversal of their party's fortunes: Donald J. Trump.

Imagine if Hillary Clinton had managed to secure an Electoral College victory to go along with her popular vote win a year ago. Had that happened, Ed Gillespie would probably be picking out furniture for the Virginia governor's mansion, and the state's Republicans would have reinforced their hold on the legislature. All over the country, conservatives consumed with rage at a Clinton presidency would be creating the second coming of the Tea Party, organizing protests, signing up volunteers, registering voters, and preparing for what would likely be a Republican wave election in 2018.

If that wave came, the Democratic Party could have wound up at one of the lowest points in its history. Democrats are already at a terrible numeric disadvantage, with Republicans controlling both houses of Congress and a majority of governorships and state legislatures. It would have gotten even worse.

But now, all the energy is on the other side. Democrats didn't just win Tuesday, they won in ways that made clear the power of the diverse coalition that Clinton had hoped would carry her to victory. That diversity was reflected in their candidates. The first transgender member of the Virginia legislature, and the first Asian-American woman, and the first two Latinas. The first African-American woman mayor of Charlotte. The first African-American mayor of St. Paul. The first Sikh mayor of Hoboken, New Jersey. The first lesbian mayor of Seattle, and the first female mayor of Manchester, New Hampshire. A transgender woman of color who won a seat on the Minneapolis City Council. An African-American lieutenant governor in Virginia, and a Hispanic woman mayor of Topeka. A Liberian refugee even became mayor of Helena, Montana.

How many of those Democrats would have won if Donald Trump were not the president right now? Not many. Even if some of them never mentioned Trump on the campaign trail, their candidacies were boosted by Democratic volunteers, donors, and voters energized by Trump.

Republicans certainly know what's happening. One GOP member of Congress after another is retiring, not wanting to brave the voters' wrath next year — and potentially strong Republican candidates everywhere are deciding to sit it out and wait for a more promising cycle. Meanwhile, the Democratic Party is overwhelmed with people who want to run for office, many of whom never contemplated doing so before Trump got elected. The progressive group Run For Something, which helps people put together candidacies, tweeted on Wednesday, "Usually, we get 10-15 new candidates signing up per day. Since polls closed last night, more than 100 young progressives have raised their hands to say they want to run." One colorful story is that of 32-year-old Ashley Bennett in New Jersey, who was incensed when one of her county freeholders shared a sexist social media meme about the Women's March that took place the day after Trump's inauguration, so she ran against him and won.

We don't know whether 2018 will be a wave election that puts Democrats back in power in Congress, but it sure is looking like a real possibility. You can even foresee a strong election for Democrats in 2020 when Trump is up for re-election — and if it goes well for them in the states, they could gain more control over the redistricting process that will happen in 2021, potentially enabling them to reverse some of the gerrymandering that has given Republicans such an advantage around the country.

But Trump hasn't just gotten Democrats angry, he also has them re-examining their way of doing business. Democrats watched Hillary Clinton try and fail to win over moderate Republicans, and many have concluded that mobilizing their own voters is much more important than trying to win the favor of those who usually vote Republican. In an age in which party affiliation has become a kind of immutable tribal identity, you just can't get very many people to cross party lines.

There's academic support for this idea: As a recent meta-analysis of multiple political science studies concluded, efforts by campaigns during general elections at persuasion — changing people's minds on their vote choice — are pretty much a waste of time. "The direct persuasive effects of voter contact and advertising in general elections are essentially zero," the authors wrote. It's a somewhat complicated picture, but the takeaway is that the better use of resources is mobilization: not converting the other side's voters, but getting your own voters excited enough to get to the polls. This year's election certainly reinforced that idea, and Democrats are taking it to heart.

In a related development, you can't help but notice a new eagerness among elected Democrats to stop splitting the difference on issues and forthrightly advocate for policies that reflect liberal values, whether it's a living wage or protecting women's right to choose or universal health coverage — which is more likely to give their partisans something to vote for, even as they want to vote against Trump.

That's not to say there aren't still plenty of internal disagreements among Democrats over both strategy and substance, because there are. But years from now, we may say that 2017 was the year when dispirited Democrats came back to life and began renewing their party, enabling it emerge stronger than it had been in years. We may even say that President Trump was the best thing that ever happened to the Democratic Party.