Young adults motivated by social issues and dissatisfied with the Trump administration turned out in record numbers to vote in the 2018 midterms and backed Democratic candidates by historic margins, initial analysis shows.

Thirty-one percent of voters aged 18 to 29 cast ballots in the 2018 midterm elections, shattering turnout rates from the past quarter century, according to an estimate by the Center for Information and Research on Civic Learning and Engagement at Tufts University. This year's turnout was at least 10 percent higher than for the 2014 midterms, according to the center's estimates.

While exact vote tallies won't be available for several weeks, the preliminary data align with pre-election surveys , which reported a record number of young voters who said they would vote.

Participation in this year's midterms started weeks ago, as young voters cast early ballots in huge swaths. In many states, the number of early ballots cast by young adults eclipsed total turnout levels in 2014, according to The Hill .

Young voters also backed Democratic candidates in historic numbers , playing a critical role in some Democratic victories and narrowing the margin in some losses, exit polls suggest. More than two-thirds of voters aged 18 to 29 voted for Democrats in the 2018 election, compared with 32 percent who supported Republican candidates.

The 35 percentage point chasm is the largest gap in at least the last 25 years and is about three times higher than it was in the 2014 midterms, according to the center. The data from the exit polls is reasonably consistent with pre-election polling.

"That kind of share difference in vote choice was not even seen in President Obama's election," says Kei Kawashima-Ginsberg, director of the center. "It's historic in that way, and that's when young people's votes really count in terms of the change in outcome."

Voter turnout and choice may have been decisive in several races, analysts say.

"In an overwhelming number of races, according to the exit polls, the Democrats won the younger vote – folks under the age of 45 – and they lost folks over the age of 45," says John Della Volpe, director of polling at the Institute of Politics at Harvard University. It's a trend, he said, that has been consistent in recent special elections as well.

In a tight Nevada Senate race, youth voters backed Democrat Jacky Rosen by large margins, helping propel her to a 5-point win against Republican incumbent Dean Heller. Young voter turnout in the state was expected around 19 percent, according to the institute, and Rosen won the under-30 vote by a gaping 37 points. She also won the 30- to 45-year-old vote by 23 points, according to exit-poll analysis by the institute. In contrast, voters over 45 favored Heller by significant margins.

Young adult voters also narrowed the race for Senate in deep-red Texas, where Democrat Beto O'Rourke mounted a long-shot run against incumbent Republican Ted Cruz. While Cruz won the race by less than 3 points, exit polls showed that an enormous 71 percent of voters under 30 backed O'Rourke.

By comparison, O'Rourke garnered 51 percent of the vote from those aged 30 to 45, while Cruz was favored by voters over 45.

The youth-vote choice in Texas was surprising, given the electorate's more conservative voting record, says Kawashima-Ginsberg. In 2016, only 55 percent of young voters supported Democratic presidential candidate Hillary Clinton, and the age group was split evenly between parties in the governor's race, she said.

"It was like a different Texas for youth," Kawashima-Ginsberg says of Tuesday's election. "In this particular election, either the candidate was really able to excite young people to come out and really support him for the entire election, or Texas's electorate is starting to shift toward a more Democratic one. This is something to watch, especially if young people are able to come out in higher numbers than usual."

Della Volpe says he and his team of researchers saw attitudes in the youth electorate shift after the 2016 general election, and young voters realized there were "real tangible differences" politics could make in their lives.

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Students at Marjory Stoneman Douglas High School in Parkland, Florida, who had coalesced around the issue of gun control after a mass shooting at their school in February, channeled their activism into efforts to get other young people to vote – a movement Kawashima-Ginsberg and Della Volpe say was essential in motivating young voters to invest in issues and get to the polls.

"I don't think that the role that the students of Parkland had can be overstated," Della Volpe says.

Della Volpe also points to the Trump administration as a motivating factor for young voters.

"This was very much, I think, for young people, a rebuke of the first two years of an administration that they don't see as sharing their values," Della Volpe says. Young Americans have held a consistently unfavorable view of the president, according to numbers from Gallup.

Issues like the #MeToo movement, reproductive rights and immigration were also a likely factor in driving young people to the ballot box, and they could have been particularly impactful in states like Texas, where migrant children have been separated from their parents, says Kawashima-Ginsberg.