What will millennials turn out for this midterm election?

What does it take to get the most liberal age group to the ballot box in November?

Millennials were crucial in President Obama's 2008 and 2012 election victories. But Democrats should be skeptical that voters between the ages of 18 and 29 will show up in similar numbers come November. There's a political generation gap that exists between presidential and midterm elections-- and it presents serious trouble for Democrats in very tight races.

A Harvard University Institute of Politics study published at the end of April reported that "less than one in four (23%) of Americans under the age of 30 say that they will 'definitely be voting.'"

"Young voter turnout is going to be the biggest drop-off in midterm elections, and that's particularly true because the presidential race makes it much easier for them to gain information and it's much more engaging," Democratic pollster Celinda Lake told CBS News.

According to Lake Research polling, 34 million fewer voters show up in midterm elections, and about 24 million of them are Democratic-leaning voters. Though young voter drop-off in midterm elections is far from a new phenomenon, Lake says that the numbers are particularly alarming because young voters seem especially disinterested this year.

"If people were paying attention to young people in an authentic way, actually caring about those issues, you'd see a much higher turnout rate," said Ashley Spillane, the executive director of Rock the Vote, a group that aims to engage young voters.

The group unveiled a music video this week starring a ballot-and-blunt toting Lil' Jon dancing to a politically-tuned remix of his song "Turn Down For What." Meanwhile, the news site Vocativ is launching an app that taps into millennials' passion for internet matchmaking and emojis to pair them with their "Senate Soul Mate."

But at a time where 90 percent of millennials always have their phone by their side, Spillane said young people feel like the political system is not accessible to them.

"We should be expanding and growing the electorate to include people doing things in different ways," she told CBS News. "And then there is the narrative that young people aren't participating, which also suppresses turnout. Young people are participating at record numbers."

But for midterm turnout, exit polling proves otherwise: in the 1978 midterms, about 20 percent of 18-29 year olds voted; in 2010, it was 12 percent.

Democrats' recent dependence on younger voters in presidential years underscores the importance of their potential to make a serious impact this year in Senate battlegrounds such as Alaska, Colorado, Louisiana, North Carolina and Kentucky.

Because Mr. Obama enjoyed ample margin of victory among young voters in the last two presidential cycles, Lake believes Democrats have not been as thoughtful about tackling the challenge of continuing to engage various subsets of young voters.

Meanwhile, Republicans have been proactive this year with their outreach to young Christian voters and first-time homeowners, she said.

For instance, the College Republican National Committee (CRNC) last week launched a $1 million digital ad campaign with a politicized version of the TV series, "Say Yes to the Dress."

The liberal New Republic mocked the ad, writing "The GOP's Sexist Reality TV Spoofs aren't going to win over female voters."

"I think that in terms of any kind of negative feedback within the Beltway and from Democrats is a result of the fact that they don't like that we are reaching out to voters that they have taken for granted for a long time," CRNC president Alexandra Smith told CBS News.

The $2 million investment that the CRNC has put into their field program is not a fool's errand, Smith said: In contested midterm Senate races ultimately won by Republicans in 2010 -- Ohio, Wisconsin, and Pennsylvania -- Republicans nearly split the youth vote with Democrats, trailing only a few points behind them.

So what is the key to disrupting the cycle of young voter recession?

John Della Volpe, the Director of Polling at the Harvard Institute of Politics, school argues there are three factors that must come together for a get-out-the-vote campaign to resonate among younger voters: mechanics, a "tangibility" factor, and an inspirational candidate.

"Young people lived through Katrina, 9-11, the war in Iraq and learned that politicians can make a difference in an individual's life and in our country - politics needs to be tangible for young people," Della Volpe told CBS News. He also pointed out that "someone needs to inspire them and they need to be asked for their help. The asking part has to come from individual members or candidates."