WASHINGTON — It’s been hard out there for young Hillary Clinton supporters, often drowned out during the primary by the shouts of their peers backing Vermont Senator Bernie Sanders and even harassed online and in person by “Bernie bullies.’’

But those young Clinton supporters are out there. Really. And as the campaign veers toward November, Clinton must ignite their quiet devotion to help her fire up more young voters.

“We exist! And we are enthusiastic!’’ said Radhika Mathur, 25, a PhD student at Harvard who has been on the “ready for Hillary team’’ since 2013.

Younger voters made up a key bloc of the coalition that gave Barack Obama two White House victories. Yet Clinton struggled with the millennial generation throughout the 2016 primary, time and again crushed by rival Sanders among young voters.

Donald Trump, meanwhile, is making a bid for disaffected supporters of the Vermont senator, playing off frustrations many Sanders fans had with the primary process. “For all of those Bernie Sanders voters who will be left out in the cold by a rigged system of superdelegates, we welcome you with open arms,’’ Trump said at his June 7 primary-night rally.

It even looks as if millennials cast more ballots for Trump than Clinton over the course of the primary, according to an estimate compiled by Tufts University’s Center for Information & Research on Civic Learning and Engagement. The Tufts count of 17- to 29-year-olds in the 20 states that provided exit polling (it excludes California, among others) showed Sanders received 1.9 million votes, Trump pulled in around 746,000, and Clinton won a little more 727,000.

One might think, given these dismal numbers and resulting media narrative, that no one under 30 would be caught dead voting for Clinton. But the former secretary of state does have a loyal, if less visible, following among the millennial set. These voters — through conversations with friends, activism on campus, or work with the Clinton campaign — could help sow the seeds for a larger crop of younger supporters for the presumptive Democratic nominee come November.

“We’re very passionate about Hillary, [but] perhaps less outspoken about it,’’ said Keith Drucker, 21, a rising senior at Boston University who volunteered for Clinton in New Hampshire. “And maybe that is a characteristic that more Bernie supporters have, that they’re a little bit louder, and a little bit more in your face.’’

Drucker, the president-elect of “BU for Hillary,’’ said many of the other volunteers he worked with were fellow millennials and they weren’t “any less supportive and motivated to work for Hillary’’ than the Sanders supporters he knows.

Obama trounced his Republican opponents among voters under the age of 30 both times he topped the ticket, capturing 66 percent of them in 2008 to Senator John McCain’s 32 percent and winning 60 percent to former Massachusetts governor Mitt Romney’s 36 percent in 2012, according to Tufts’ Center for Civic Learning and Engagement.

The Clinton campaign is ramping up outreach efforts to voters 35 and younger, recently announcing several hires dedicated to motivating millennials. The new team includes Kunoor Ojha, who served as the Sanders campaign’s national director of student organizing.

Such campaign nuts and bolts are important, said Tufts professor Peter Levine. “There’s a lot of evidence that young people respond to being contacted, to outreach,’’ he said. Reporting showed that Sanders undertook “a really intense job with highly skilled people at outreach to youth,’’ and that’s an area where Clinton “can emulate him — and has to.’’

Still, persuading Sanders’ legions of young followers to get behind Clinton will be a challenge, given the fevered pitch of pro-Sanders passions. During much of his campaign, Sanders sought to portray Clinton as a tool of Wall Street and other business interests, and some Democrats worry the impression he painted will not fade.

Several young Clinton supporters interviewed by the Globe reported tensions with peers backing Sanders, and some reported even being attacked for being a Clinton supporter.

At the University of Michigan, Anushka Sarkar dealt with people screaming insults such as “Benghazi killer’’ and “liar’’ when she walked across campus wearing a pro-Clinton T-shirt. Others said their online posts about Clinton were greeted with four-letter words and similar hostility.

Mathur, the Harvard graduate student, said her experience as a pro-Clinton Reddit user was “pretty horrible.’’ The online discussion site works under a voting system that controls the visibility of links and comments. If other “redditors’’ don’t like your submission they “downvote’’ it, making it effectively invisible to others.

“You’re quite literally silenced if you’re a Hillary supporter,’’ she said, while negative stories about Clinton dominate on the political threads. (Recently, one of the top stories on the general political forum was about how Clinton could get 10 years in prison if indicted and convicted for actions involving her use of a private e-mail server as secretary of state.)

In January, Mathur banded together with some other Clinton supporters on the site and created a pro-Clinton forum where they as moderators could help create a community. “We did have to ban a lot of trolls — so much banning — in order to keep it pro-Hillary,’’ she said.

Young voters love Sanders for his promises to overhaul a corrupt system from which they felt alienated and believe he was engaged in something bigger than a same-old political campaign, polling suggests.

Those who embraced Clinton, in interviews, generally cited far less sexy motivations — the thoroughness of her policy prescriptions, the pragmatism of her approach to turning those plans into reality, and her track record of getting things done.

“To me, I don’t care if a policy is exciting. I care if it’s effective,’’ said Emily Moss, 19, a rising sophomore at Clinton’s alma mater, Wellesley College. She said she understands why many young voters found Sanders’ calls for political revolution more thrilling than Clinton’s approach of incremental change. The latter is harder to get excited about if you aren’t as wonky as she is, Moss admitted.

“All you ever hear about her is all the negative stuff that happened,’’ said Leah Dougherty, 29, who lives outside Denver. “All these supposed scandals, current scandals, etcetera, but nobody seems to focus on her actual work ethic and what she’s accomplished over the past, what is it, 25 or so years she’s been in the public eye.’’

Sarkar, the Michigan student, has admired Clinton since she watched Clinton announce her 2007 exploratory bid for president. Still, the 19-year-old pushed herself “to explore the other options, and I still came back to her,’’ she said.

Sanders planned to pay for each and every one of his policy proposals by taxing the rich, Sarkar said. “If it were that easy, it would be done by now.’’

More than three in five 18- to 29-year-olds wanted to see a Democrat prevail in the November election, according to a poll released in April by Harvard University’s Institute of Politics at the John F. Kennedy School of Government. And while Sanders was the most popular candidate among the age group, 61 percent of likely voters said they would vote for Clinton in a head-to-head matchup against Trump, while only 25 percent said they’d vote for the real estate mogul.

Among young voters who viewed Sanders favorably, 80 percent said they would vote for Clinton.

Moss, who will co-lead a student-run pro-Clinton group at Wellesley in the fall, said she believes Trump “can be a huge unifying force’’ for Democrats, and it’s a theme she said they will emphasize in their work for the candidate. “Young people, even more so perhaps than other generations, have a greater potential to unite against Trump’s bigotry. There’s a huge consensus in the millennial generation that that’s just fundamentally unacceptable.’’

Victoria McGrane can be reached at vicki.mcgrane@globe.com.