Hillary Clinton greets the crowd along with Senator Bernie Sanders during an event in which she was endorsed by Senator Sanders at Portsmouth High School on Tuesday, July 12, 2016 in Portsmouth, New Hampshire. (Bryce Vickmark/Zuma Press/TNS)

Now that school is back in session, college campuses are becoming ground zero for Democratic candidates seeking to woo young voters and tap into the enthusiasm Vermont Sen. Bernie Sanders generated during his presidential campaign.

New Hampshire – with just four electoral votes – is one of a handful of battleground states that could decide the presidential contest in November. And millennial voters, who make up roughly 20 percent of the state’s electorate, could help tip the scales. Young voters aged 18 to 29 overwhelmingly supported Sanders in the primary, showing up by the thousands to campaign rallies that had a vibe more akin to a rock concert than a political event.

Democratic nominee Hillary Clinton is seeking that support, and she will campaign along Sanders at the University of New Hampshire today. The visit comes less than a week after Massachusetts Sen. Elizabeth Warren rallied students at the Durham campus with Democratic Gov. Maggie Hassan, who is seeking to unseat Republican U.S. Sen. Kelly Ayotte.

“Democrats are looking at this as an opportunity to tap into a demographic that typically doesn’t turn out in huge ways, but that could really be a difference-maker for them on Election Day,” said New England College political science professor Wayne Lesperance.

UNH’s Durham campus is the largest in the state, boasting more than 15,000 students in 2015.

Sanders won Durham in the primary with more than 70 percent of the Democratic vote, and students said they were largely drawn to his message of free college tuition and plans to get big money out of politics.

Elena Ryan, co-president of UNH campus Democrats, didn’t say whether students drawn to Sanders in the primary have fully shifted to Clinton or other candidates altogether.

But she did say the prospect of President Donald Trump is “really scary” to students. And she does expect Sanders’s popularity at UNH to boost participation in the November election.

The Vermont senator drew new students into the political process who, having supported him in the primary, are already registered to vote, she said, making it easier for them to show up to the polls in November.

“He really did light a fire with the younger voters,” Ryan said. “It got a level of preliminary engagement with people, where they actually wanted to understand what was going on. I don’t think that has left in any way.”

Democrats typically do well among voters aged 18 to 29. President Obama won the demographic by a 32-point margin in 2008 and by 24 points in 2012. While Obama’s support among young voters slipped nationally between the two elections, it grew in New Hampshire. Obama won the youth vote by 28 percentage points in 2012, up from a 24-point margin four years earlier.

But young people are one of the least reliable voter groups to show up to the polls. Peak voter turnout was in 2004 and 2008, when 47 and 49 percent of young people voted, respectively. In 2004, young voters represented just 14 percent of the electorate, and that jumped to 18 percent in 2008.

Sanders outperformed the former secretary of state most dramatically among millennials in the state’s February primary. He earned 83 percent of votes cast by 18- to 29-year-olds, compared with Clinton’s 16 percent, according to exit polls. Clinton bested Sanders only among voters over age 65.

It remains to be seen whether young voters will show up at the polls and back Clinton in large numbers come November.

A national McClatchy-Marist poll from August shows Clinton leading Trump among young voters 53 to 17 percent. Trump’s popularity among young voters plummets when third-party candidates Gary Johnson and Jill Stein are included. Then, Trump wins 9 percent of the vote to Clinton’s 41 percent, Johnson’s 23 percent and Stein’s 16 percent, the poll found.

Johnson and his running mate, former Massachusetts governor Bill Weld, will follow Clinton to UNH tonight, as part of the “Hardball College Tour,” which will be broadcast on MSNBC.

(Allie Morris can be reached at 369-3307 or amorris@cmonitor.com.)