More than half of all voters under the age of 30 cast a ballot in this year’s elections, an unprecedented level of engagement that likely cemented President-elect Joe Biden’s Electoral College victory in critical swing states.

Between 52 percent and 55 percent of eligible adults under the age of 30 voted this year, according to estimates by the Center for Information and Research on Civic Learning and Engagement at Tufts University.

Four years ago, the center estimated that between 42 percent and 44 percent in that same group cast a ballot. Even in 2008, when young adults turned out at record levels to back then-candidate Barack Obama, those records hovered around 48 percent.

“We will exceed that number, and it may not be even a question,” said John Della Volpe, director of polling at Harvard’s Kennedy School of Government, who took leave to work for Biden’s campaign polling younger voters. “We will have seen, two elections in a row — the midterms in ’18 and the presidential in ’20 — historical, unprecedented youth participation.”

The younger voters who turned out this year favored Biden over President Trump by huge margins; exit polls found 60 percent of voters under 30 backed Biden, 5 percentage points higher than the percent who backed Democratic nominee Hillary Clinton in 2016.

Analysts who track voting statistics caution against relying on exit polls, but early data from some states that have released final turnout data confirms the surge in younger turnout. Six states — Colorado, Georgia, Montana, Nevada, Oregon and Washington — have already made public information about who voted this month.

“Every one of them has shown a pretty significant youth surge over 2016,” said Tom Bonier, chief executive at the Democratic data firm TargetSmart Consulting. “The increase in turnout among younger voters was greater than the increase overall.”

Biden won younger voters in at least 31 states, according to the Tufts estimates, while Trump won the youth vote in only seven states. Data for the remaining dozen states, none of which are presidential battlegrounds, has not yet been released.

Conscious that Clinton had not maxed out support among younger voters, who might have been drawn more to Sen. Bernie Sanders (I-Vt.), the Biden campaign made a special effort to heal the wounds of the primary campaign season, and to introduce their candidate to voters who would not win in a primary, but needed in November.

“What was unique about the youth vote is that we needed to share the president-elect’s vision and background to a generation that didn’t have a relationship with him when he was in the White House,” Della Volpe said. “It was really about finding the time and the space to connect with the other wing of the party that hadn’t taken a look at him yet.”

In the key battlegrounds, those younger voters likely netted Biden enough votes to carry the Electoral College. Based on turnout and exit poll data, the Tufts center estimates voters under 30 gave Biden enough net votes to carry Arizona, Georgia, Pennsylvania — and even Michigan, a state Biden won by a relatively comfortable 148,000 votes.

Biden’s margins were especially strong among young voters of color. He won more than 80 percent among both Black and Asian young voters, and nearly three-quarters of the young Hispanic vote. Biden led Trump by 6 points, 51 percent to 45 percent, among younger white voters.

Younger voters were more likely to cite environmental issues and the threat of climate change, gun control and opposition to a wall along the border with Mexico as their chief concerns than were older voters. In a pre-election survey, more than half, 52 percent, said they had lost work or income because of the coronavirus pandemic.