Supporters of Democratic presidential candidate Bernie Sanders cheer during a rally at Macomb Community College in Warren, Michigan, March 5, 2016. Geoff Robins | AFP | Getty Images

Desiree May is feeling the Bern. Ever since the 27-year-old graphic designer saw Democratic presidential candidate Bernie Sanders speak at a Madison, Wisconsin, event in July, she's been volunteering for his campaign. "Just the passion in that room was unbelievable, and Bernie's integrity is really appealing to me and inspiring," May said. May estimates she spends four hours each weekday knocking on doors canvassing and encouraging people to vote in her hometown of Green Bay, as well as another hour running various Wisconsin-focused Sanders social media accounts. On weekends, her volunteer work takes up the entire day. "His dedication to his message is really moving," she said. "I want more people to be aware of who he is and what he stands for." About one-fifth of Americans have attended a political event in the last year, according to a new survey of more than 3,000 adults in the U.S. by Eventbrite and Ipsos. Among those attendees, 45 percent are millennials. The online survey was conducted Feb. 3-6 and had a margin of error of 2.1 percentage points. Millennials are more than bodies at events: If you can get them to turn up, they show sustained interest. Millennials as event goers were almost twice as likely to volunteer for campaigns than were Gen Xers, and more than twice as likely versus baby boomers. They were also 33 percent more likely to donate, compared with 20 percent for Gen X and 24 percent for boomers. And, 22 percent were more likely to host their own candidate event, compared with only 10 percent and 2 percent of their respective counterparts. "In some ways (millennials) aren't focused yet, but they will understand that issues that will be decided in November will affect them a great deal," said Rob Shepardson, co-founder and partner of marketing communications agency SS+K . "There's a bit of (painting) with a broad brush that young people aren't interested. They are quite interested in issues that affect them."

The youth have always been the most likely to attend political events — they have the time and energy. However, unlike previous generations, millennials in particular value experiences over material goods. Eventbrite and Ipsos found that 56 percent of millennials would more likely meet a candidate in person at an event than engage with them on social media. "Millennials are not about the collection of things, but about the collection of experiences. … If you think of what drives them to be engaged, it's the idea of the in-person event experience," said Chad Barth, senior political and government relations manager for Eventbrite. This obsession with going to events and being seen there through social media posts could be traced to the 2008 recession, said Wilson Standish, a director at OMD Worldwide's Ignition Factory. With the lack of jobs and money available, millennials figured that they might as well spend their time doing something that makes them happy, he said. Standish hypothesized that that led to a rise in millennials doing jobs with their hands or seeking work outdoors. Collecting experiences became important — and financially more likely — than collecting objects. "We've seen many millennials would take more vacation time than a pay increase," Standish pointed out. "All these things show there's a higher valuation in experiences across the board because the economy of work doesn't pay out as much as it did for them as for boomers and Xers." Add to this millennials' love for belonging to a community, and political events become the place to be, Standish said.

Desiree May decided to volunteer for the Bernie Sanders campaign after seeing him speak at a Wisconsin event. Courtesy of Desiree May.

Shepardson, whose firm was the youth agency for the Obama campaigns in 2008 and 2012, added that millennials are more likely to show excitement for a campaign and can influence the political opinions of their older siblings or parents.

"It's known as reverse aspiration, or when older folks of a certain age want to make sure they are paying attention to what is cool," he said. Then there's social media. The candidate millennials follow the most on social media is Sanders (51 percent), but Hillary Clinton and Donald Trump also have high numbers — 44 percent and 31 percent, respectively, Eventbrite and Ipsos found. More importantly, posts about candidates and from political events become free, effective political advertising — and millennials love posting those pictures and using hashtags. The Eventbrite/Ipsos study showed millennials who are willing to attend events are more likely to post about it on social media. Six in 10 rallygoers were more likely to engage in political conversations on social media, versus 37 percent of average attendees. "There's a lot of skepticism about institutions, including the media and including advertising," said Shepardson. "If people are feeling that they are getting the unvarnished truth from a source they trust or like on social media it goes a long way. Not all social media people are very sophisticated in editing around the crackpots. If it's on the newsfeed of people they like and respect, that is about the best you can hope for."