ANALYSIS: Issues and Trump drove voters to Democrats, but will those voters swing back?

Who showed up to vote in an off-off year tells only part of the story.

They came out in droves to vote against him.

A surge in liberals and minority voters changed the makeup of the electorate compared with a year ago, and white women, especially those with a college degree, swung away from this White House.

By 2 to 1, voters in Virginia said they were casting their ballots to show opposition to the president rather than support for him, according to ABC News' exit polls. In New Jersey the ratio was nearly 3 to 1.

"Yesterday truly was a referendum on [Trump]," a senior staffer for Virginia Republican gubernatorial candidate Ed Gillespie told ABC news.

But who showed up to vote in an off-off year tells only part of the story.

Democrats now have evidence — hard data and powerful personal stories — to show that their grass roots enthusiasm has reached new heights in the era of Trump.

In Virginia their share of the electorate was up 4 points from last year.

Nearly half the voters in the state, 47 percent, said they strongly disapprove of the president, and of that group, 95 percent voted for the Democratic candidate for governor, Ralph Northam. That suggests that voters had no hesitation tying Gillespie to Trump — and not in a good way.

A pollster who consulted with the Gillespie campaign told ABC, "GOP is in real trouble in 2018 if Dems are able to mobilize like they did yesterday for the midterms. Everyone thought turnout would look more like 2013 than 2016, so [it will be] interesting to see if off-year Dem excitement advantage can carry through to next November."

Plus, the diverse group of newly elected Democrats nationwide looked and felt like a pointed rejection of Trump's often racially charged rhetoric.

A Sikh who wears a turban faced an attack ad that used the word "terrorist" above his picture. He was elected mayor in Hoboken, New Jersey, last night.

Manka Dhingra, the woman who flipped the Washington state Senate from red to blue, is also a Sikh. Like many of the women on ballots around the country, she said last year's election motivated her to get involved in politics.

"We see the politics of tribalism, misinformation and mistrust happening all around us. We see the hate and fear and division walking around," she said. "But in the face of all of those facts, the community came together … We responded with love."

Virginia voters not only gave the thumbs up to Danica Roem, an openly transgender woman, but they also picked her to replace the author of the state's so-called bathroom bill, a man who described himself as the state's "chief homophobe." His measure would have restricted which bathrooms transgender people may use.

Context is key, and last night's fights mostly played out on Democratic-friendly terrain. Sure, Democrats picked up a number of state legislature seats in Virginia, but the state has been trending blue over the last few years.

The White House tried Wednesday to shrug off the night and argued the results were not about Trump. A person familiar with his political operation said "inaction in Washington is to blame."

"These are practical voters," that person said of the overwhelmingly Democratic turnout in Northern Virginia. "These voters are frustrated by the lack of action from Congress. These are voters that will bounce back."

The fact that voters named health care and gun policy as the issues that mattered most to them could have implications for candidates in parts of the country that skew Republican.

As a doctor, Northam was particularly well positioned to capitalize on Virginia residents' anxiety about health care, and he leaned in on the issue.

He accused Republicans of trying to strip away coverage. His methods may be a model for other Democrats.

Gun control activists said this was huge.

So the Democrat's success in this space, activists said, is evidence that some people came out looking for stricter gun control policies.

"Gun violence is a third rail no more — and we will carry this momentum into 2018 midterms," said John Feinblatt, the president of Everytown for Gun Safety.

The group endorsed seven candidates for the state legislature, and all of them won.

ABC News' Meridith McGraw and Tara Palmeri contributed.