Youth vote enthusiasm has doubled since the last midterm cycle, and that's very bad news for the GOP.

The chant of “vote them out” rang out during last month’s March For Our Lives event in Washington, D.C., as hundreds of thousands of activists protested for gun safety. Millions more participated around the country and the globe.

In fact, nearly 5,000 new voters, most under the age of 30, registered to vote the day of the March for Our Lives rally.

And it’s not just anecdotal; the youth vote could be a major factor in this year’s midterms.

A new Harvard Institute of Politics poll suggest that “vote them out” mantra is now a driving force in American politics, especially among young Democratic voters. This, as the student survivors from the Parkland, Florida, school gun massacre continue to reshape political activism in 2018.

And right now, the enthusiasm is sky high.

Young Democrats are driving nearly all of the increase in enthusiasm; a majority (51%) report that they will ‘definitely’ vote in November,” Axios reports.

That represents a gigantic gain from the 2014 midterm cycle, when just 28 percent of young Democratic voters (ages 18-29) were “definitely” going to vote.

Nationally, only 20 percent of voters ages 18-29 cast votes in the 2014 midterms, the lowest ever recorded, according to the Miami Herald.

One of the hurdles the Democratic Party has faced for years is a weak turnout during midterm elections. All indications are that 2018 will represent a dramatic change, especially among younger voters.

Marjory Stoneman Douglas High School student activist David Hogg is taking a gap year and not attending college in the fall so that he can help work on midterm elections and educate voters.

It’s likely that Hogg and his fellow Parkland activists will be heavily involved in the Florida Senate race, pitting Democrat Bill Nelson against Republican Rick Scott. As governor of Florida, Scott was known as an NRA yes man, and signed into law some of the most radical, pro-NRA guns laws in the country.

Students are getting some help too. Tom Steyer, the billionaire former hedge fund executive, announced in January he was putting $30 million into getting out the youth vote, with a heavy emphasis on Florida.

Parkland activists have already made their presences felt in campaigns nationwide.

Last month, when a Republican candidate for the Maine state House called Parkland students Emma Gonzalez a “skinhead lesbian” and Hogg a “moron” and a “baldfaced liar” on Twitter, he had to drop out of the race because the backlash was so strong.

Meanwhile, the new Harvard youth poll comes just one day after a Reuters survey found that Republicans are leaking voters on the other end of the age spectrum — white, educated, older voters are moving away from the GOP.

In fact, there’s been a 12-point swing toward Democrats among that crucial voting bloc.

Vote them out, indeed.