One of the most important political stories in recent years has been the growth of the Hispanic electorate. This year, the question is not only how many Hispanics will vote, but whether the GOP is at risk of losing their support for a generation.

The National Association of Latino Elected and Appointed Officials (NALEO) predicts that 13.1 million Hispanics will vote this fall, up from 11.2 million in 2012. That’s a big increase. Still, it means fewer than 50 percent of eligible Hispanics are voting.

Even as their share of the electorate continues to grow, Hispanics are not voting at the same rate as other racial or ethnic groups. In 2014, only 27 percent of eligible Hispanics voted. That’s their worst single showing ever in a midterm election.

Hispanics tend to vote at lower numbers for several reasons. For one thing, the median age among Hispanics born in the U.S. is just 19. As with their Anglo or African-American peers, Hispanic youth are harder to mobilize than older voters. “Latino turnout has a lot to do with demographic factors -- a higher percentage of young, low-income and less-college-educated people,” says Cristina Beltrán, director of Latino studies at New York University. “All of these factors depress turnout for all citizens.”

Another factor is that the concerns of Hispanic voters are often ignored by national candidates -- at least, those who don’t live in swing states, says Arturo Vargas, NALEO’s executive director. This year, Democrats are gearing up to spend $15 million on Hispanic outreach in the swing states of Colorado, Florida and Nevada. “Where you have seen upticks in mobilization is where you have seen outreach by particular candidates, mostly on the Democratic side,” says David Damore, a political scientist at the University of Nevada, Las Vegas.

Democrats are hoping that Hispanics nationwide will be mobilized by the presidential candidacy of Donald Trump, who has made a number of insulting comments about immigrants and Hispanics in general. There’s even evidence suggesting many Hispanics are motivated to become citizens in order to vote against Trump. Applications for naturalization are up 14.5 percent this year.

The real growth in the Hispanic vote, however, comes from young people turning 18 -- 800,000 of them each and every month. “There are 4 million more Latinos eligible to vote in November than there were in 2012,” Vargas said. “Of those, 3.1 million are Latinos who have turned 18.”

Whether the source of new voters is naturalization or adulthood, Republicans have to worry about losing their support. The GOP share of the Hispanic vote has gone down every four years since 2000. In 2012, Mitt Romney took just 27 percent of the Hispanic vote. An official Republican report after that election stressed the need to appeal to Hispanics, but the party nominated Trump instead, whose polling numbers among the group are dreadful. “Latinos are a permanent part of the political landscape in this country,” Vargas says. “Candidates that don’t recognize that and don’t act on that are not going to be successful.”