CHICAGO – A surge in early voting totals in key states across the nation suggests that 2018 could be the year that young people finally show up for a midterm election.

For decades, older voters have dominated the electorate in non-presidential years. But early and absentee voting among youth aged 18 to 29 has increased dramatically in several states with hotly contested races – including Arizona, Florida, Georgia, Illinois, Nevada and Texas – compared to the 2014 midterm races.

Early youth voting in Illinois is up 144 percent over the 2014 midterms. More than 70 percent of the 6,200 undergraduates at the University of Chicago registered to vote through the TurboVote app. At the university’s early voting site, students waited up to an hour to cast their ballots.

First-time voter Eric You, 18, spent Halloween dropping bags of candy at the doors of fellow University of Chicago students that included a very millennial-worded reminder: Don’t ghost the vote.

You, a member of the university’s non-partisan UChi Votes initiative, said his motivation is simple.

“I want there to be a check on this president,” You said.

If the early youth voting trend holds up, it could bolster Democrats’ chance of picking up the 23 seats they need to take control of the House and win several gubernatorial races, according to a Harvard University Institute of Politics poll published last week. Polls suggest Republicans could add to their 51 to 49 margin in the Senate.

Forty percent of the young voters responding said they would "definitely vote" in the midterms, the Harvard poll found. Fifty-four percent of Democrats indicated a high likelihood of voting; 43 percent of Republicans indicated a high likelihood.

Less than 20 percent of young people bothered to vote in 2014. That was half the rate of the general population.

Early voting data ahead of Election Day suggests that this year could be different.

More than 35 million Americans have already cast their midterm election ballots, a 75 percent increase over the roughly 20 million who cast ballots ahead of Election Day 2014.

Nationally, voters aged 18 to 39 have nearly tripled their early voting rate since 2014. That's increased their share of the early vote by more than 3 percentage points.

The early voting share of voters aged 50 to 64, meanwhile, has fallen by more than 2.5 percentage points. The share of those 65 and older has fallen nearly 5 points.

In Georgia, where Democrat Stacey Abrams is looking to become the first black female governor in the nation’s history, youth voters cast nearly 215,000 ballots as of Saturday – a 362 percent increase over the same point in the 2014 election, according to TargetSmart, a Democratic political data services firm.

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In Nevada, where Republican Sen. Dean Heller is locked in a close race with Democrat Rep. Jacky Rosen, young voters have cast more than 56,000 ballots, a 409 percent surge in early and absentee voting.

Nearly 300,000 young Floridians cast early ballots, a 111 percent increase over the 2014 turnout.

The state has two marquee races. For governor, polls show Democratic Tallahassee Mayor Andrew Gillum has a slight edge over Republican Rep. Ron DeSantis. The seat is currently held by Republican Gov. Rick Scott.

For the Senate, polls show Scott closely trailing Democratic incumbent Bill Nelson.

Voters in the Sunshine State are younger, more racially diverse and less likely to belong to a political party than in any time in recent decades, a USA TODAY Network analysis found.

Seventy-six percent of voters 65 or older are non-Hispanic whites. Just 50 percent of Florida voters under 30 are.

Young voters have made up about 6.8 percent of early voting and absentee voters in Florida. In 2014, they made up about 4.8 percent. The share of early voters 65 and older has fallen to 44.6 percent, down from 47.8 percent in 2014.

Susan MacManus, a retired political science professor from the University of South Florida, predicted that young voters would decide the state's races. A large youth turnout would help Democrats; if they largely stay at home, Republicans will gain.

"They are going to make one person the winner," she said. "Or they are going to make the other person the winner."

The number of people newly registered to vote in Arizona this year is more than double that of the last midterm election year, data from the secretary of state's office shows.

The youngest voting demographic, those aged 18 to 24, leads all other age groups in new voters registered since Jan. 1. Early voting among Arizona voters is up about 186 percent as of Friday compared to same point in 2014 midterm.

In Missouri, one of 13 states that does not allow early voting or casting an early ballot without a valid excuse, Democratic and Republican students at the flagship University of Missouri worked with a nonpartisan student lobbying group to register more than 2,000 students this fall.

In the Show Me State’s most closely-watched contest, Democratic Sen. Claire McCaskill is fighting a challenge from Republican state Attorney General Josh Hawley. Polls show Hawley with a slight lead in the state that President Trump won by nearly 19 percentage points in 2016.

Kayla Everett, who heads Missouri’s College Democrats, said Trump’s 2016 victory switched on a light bulb for many students who previously paid little attention to politics – particularly young women.

“Following 2016, the mood on campus has been different,” she said. “Young people are more engaged, and they recognize that they need to be more aware of what’s going on.”

Maxx Cook, the president of Missouri’s College Republicans, said that his organization has seen an uptick in students coming to the group's events. College campuses, tend to tilt to the left, but Cook said the current generation is more open-minded about political ideology than those in the past.

“There’s energy with this election among young people,” he said. “But I think we have to wait and see where the young votes go.”

Contributing: Rachel Leingang and John McCarthy

Follow USA TODAY national correspondent Aamer Madhani on Twitter: @AamerISmad