But winning over the current crop of young adults -- millennials -- won't be easy. They are more liberal than their parents, even when they identify as Republican. They rely heavily on social media, to which the GOP has been slow to adapt. And although several Republican candidates and the party itself are trying to appeal to them, some of the youngest party members say they simply aren't feeling the love.
"Personally, national party leaders have been relatively non-existent in response to our generation," said Alexander Staudt, 21, a University of Iowa senior and president of Students for Rand Paul. "This is one thing that disappoints me, that our age group has effectively been disenfranchised due the general lack of motivation by party leaders to drive the youth to vote."
Traditionally, young adults vote in smaller percentages than their elders. But in a tight election, their vote can make a difference. In 2012, 60% of voters under 30 voted for President Barack Obama, giving him the edge he needed to defeat Republican Mitt Romney.
That explains why, this time around, the Republican Party and many GOP candidates are working harder to appeal to young voters. The Republican National Committee has posted on its website profiles of young adult campaign workers, or "GOP Millennials," photos of young people attending debate parties and registering voters and a link for college students to become "Campus Captains" to educate their classmates on Republican candidates.
Individual candidates and their supporters also are working to attract millennials, the generation born after 1980. Sen. Rand Paul of Kentucky launched an 11-campus college tour to connect with students. The campaign of retired neurosurgeon Ben Carson has a group called Students for Carson, which regularly hosts debate parties at college campuses. Businesswoman Carly Fiorina appeared in a well-received video on BuzzFeed, a news site popular with younger voters. And a student at Claremont McKenna College in California started the Millennials Rising PAC, a super PAC that supports former Florida Gov. Jeb Bush.
A number of Republican candidates are taking steps to reach millennials through social media, said Kei Kawashima-Ginsberg, director of the Tufts University Center for Information and Research on Civic Learning & Engagement (CIRCLE), which studies young people's political engagement.
Carson has aggressively engaged social media and has more Facebook fans -- upwards of 4.87 million -- than any other candidate. Fiorina and Trump have hosted live chats on Periscope, an app popular with millennials. And arguably, no candidate's Twitter account is more active than Donald Trump's.
Matt Moore, a millennial who is chairman of the South Carolina Republican Party, crowed about the latest GOP outreach efforts.
"The RNC's leaders, especially Reince Priebus, really get it. That's why you are seeing such innovative ideas on connecting with young voters," said Moore, 33, one of the youngest members of the Republican National Committee. "The RNC has opened an office in Silicon Valley not only to attract the best and brightest tech minds to the political arena, but to show our commitment to the innovation economy."
Nevertheless, Republicans face a number of challenges. Millennials are more liberal than any other age group, and even those who are Republican or who grew up in conservative households consider themselves more progressive than their parents, particularly on social issues, according to the Pew Research Center. Young conservatives are more likely than their older counterparts to support gay rights, immigrants and environmental regulations, positions more closely aligned with the Democratic Party.
Some millennial Republicans say they have trouble getting the party elders to hear them. Lilia Dashevsky, 18, a former chair of the Arizona Teenage Republicans, said helping the old guard understand their progressive positions on social issues is a major challenge for younger conservatives.
"Many people are hesitant to listen to us or even give second thought to our opinions and beliefs because they are different from the Republican 'norm,'" she said.
"We should be the open-tent party; it is extremely attractive for young people to feel included and accepted," Dashevsky added. "We are all about social inclusion and listening to opposing ideas while formulating our own thoughts based on our personal experiences."
That vision of an open-tent party has taken a beating during a year in which various Republican candidates have advocated building a wall to keep out immigrants, deporting undocumented immigrants and preventing Syrian refugees from settling in the U.S.
Perhaps there is one issue that best illustrates the challenges Republicans face in winning over millennials: More than 60% of young Republicans support same-sex marriage, Pew reported.
Every one of the Republican presidential candidates opposes it.
Candidates' positions aside, Republicans start out at a numerical disadvantage among young voters. Millennials are the most Democratic of any generation, Pew found. Slightly more than half (51%) of them identify as Democrats or lean Democratic, while just 35% are or lean Republican.
"President Obama won two terms due to his overwhelming success among young and minority voters," said Moore, the South Carolina Republican chair. "In 2016 and beyond, our party faces a demographic tidal wave unless we get ahead of it."
Despite the obstacles, the candidates see some openings. For instance, like Republicans in general, many millennials are economic conservatives. In fact, this generation is the most fiscally conservative since the Great Depression, preferring to save rather than invest their money, according to a study by UBS Wealth Management Americas.
"Students are graduating from college with very bleak job prospects and, in most cases, very high debt," said Garrison Coward, the 25-year-old political director for Rep. Rob Wittman (R-Virginia). "We are running the risk of being the first generation that may not do better than our parents' generation."
Sen. Marco Rubio, of Florida, is responding to that sentiment both in his language -- he talks a lot about creating a "New American Century" -- and in his policy proposals. He is proposing to reduce student debt by establishing repayment plans that are based on income. He also promotes the "sharing economy" -- businesses such as Uber and AirBnB that are popular with millennials because they offer peer-to-peer exchanges as a fiscally conservative alternative to the traditional way of doing things.
"Marco's message about a New American Century obviously speaks directly to the hopes and dreams of young Americans," said Rubio's communications director, Alex Conant. "The entire purpose of our campaign is to ensure that future generations of Americans have the same opportunities to achieve the American Dream that our parents and grandparents did."
In addition, many of the millennials who say they "lean Democratic" actually are independent voters.
"Most millennials are not familiar with party structures; they just want to be involved," Coward said. "So it is important for us to find non-conventional ways to get millennials involved in the sometimes mundane party processes, especially on the state levels."
Therein lies another problem. Across the partisan divide is a candidate who is something of a superstar among the young adult crowd. And even if he doesn't win the Democratic nomination, Sen. Bernie Sanders has tapped into a passion among millennials that could accrue to the party's ultimate nominee.
Sanders, a septuagenarian who represents Vermont, has addressed large crowds on college campuses as he rails against income inequality, advocates free tuition at public colleges and universities and argues that the government should reduce the burden of student loans. He also has met with millennials who are pushing for criminal justice reform.
"Our campaign attracts millennials because we've put forth an aggressive agenda that speaks to the real and pressing needs of young people: Make college affordable, create jobs to reduce high youth unemployment and fight climate change for future generations," said Kenneth Pennington, Sanders' digital director.
"It doesn't take much to sell Bernie's agenda to young voters. We just need to get it in front of more people."
Democratic frontrunner Hillary Clinton is working to reach millennials through an aggressive use of social media, by appearing on late-night talk shows and rolling out more than 100 Students for Hillary chapters across the country, said Xochitl Hinojosa, a campaign spokeswoman.
"The campaign has made it a priority to engage millennials through policy positions like marriage equality, college affordability and addressing student debt, climate change and providing people with economic opportunity, including increasing wages," she said.
The Recipe for Success
In the end, it will be up to the candidates to show millennials they care about them and about the issues that most concern young adults, said Kristen Soltis Anderson, author of The Selfie Vote: Where Millennials Are Leading America (And How Republicans Can Keep Up).
"Ultimately, the GOP's success with millennials will come down to the nominee and the extent to which he or she makes millennials a priority," she said. "I believe most Republicans now understand that they can't lose young voters by 20-plus points and still expect to win the White House, but it remains to be seen if they will do what it takes to win them back."