While Election Day is still just over two weeks away, more than 5 million people have already cast ballots in this year's midterm general election, with a number of states experiencing record levels of early voting.

In Indiana, home to one of the most crucial U.S. Senate contests in the country, residents in centrally located Hamilton County are casting ballots at a rate equal to the 2016 presidential election. In Minnesota, which is hosting a trio of competitive U.S. House races, early voting statewide has thus far surpassed ballots returned in 2016.

And in Georgia, which is featuring one of the most competitive governor's races of the year, ballots are being returned at three times the rate of the 2014 midterm.

More than half the country is already voting and experts say the surge ahead of Election Day leads to one likely conclusion: Overall turnout is going to spike.

"We're going to have high turnout," says Michael McDonald, a University of Florida political science professor who meticulously tracks the early vote . "You'd have to go back to the founding of the country to see presidential turnout rates during midterm elections. In some states, it's possible, if the trajectory holds up."

McDonald is forecasting a national turnout rate between 45 and 55 percent, which even at its low end would easily trample 2014's abysmal showing of 37 percent, the worst turnout since 1942, partly due to a lack of competitive races at the top of the tickets in the largest states. The last midterm that nears his forecasted rate was in 1966, when 49 percent of the country's eligible voters cast ballots.

And while the early ballots only represent a fraction of the total vote, McDonald says that, historically, early voting actually increases as more time passes.

"These numbers are just going to continue to really accelerate," he says. "You don't see it taper off."

On Monday, more than a half-dozen states and the District of Columbia began early voting, with a flurry of candidates holding rallies to encourage the practice. In Florida and Texas, thousands camped out overnight to be among the first throngs to vote in their states. The Houston Chronicle described the turnout as "shocking," citing a line of nearly 2,000 at one city voting location.

A band of new laws and a new emphasis by campaigns help explain the early voting explosion. And then, of course, there's President Donald Trump, who inflames passions in partisans of both stripes.

Paul Bentz, an Arizona-based Republican consultant, says he incentivizes his targets to act by telling them he'll stop bothering them.

"We tell people, 'If you want to be left alone, stop the mail, stop the calls, mail your ballot in,'" Bentz says. "Once you get off the ballot list, we leave you alone, we take you off our list."

In Arizona, where early voting began on Oct. 10, nearly 400,000 have returned ballots.

Republicans are holding a 12-point edge in early ballot returns , leaving Bentz to believe that the much-hyped Democratic "blue wave" hasn't materialized in the Grand Canyon State. He says a GOP ballot edge of 12 to 14 points reflects a typical midterm year in Arizona.

"We were all thinking we'd see a better than usual Democrat turnout. A couple days in, we aren't seeing it yet," Bentz says. "You know how before the tsunami comes, the beach recedes. We're not seeing any water at the beach receding."

Still, that could change as early voting continues in the state through Nov. 2. Sen. Bernie Sanders is scheduled to appear in the state on Tuesday to help prod Democrats to the polls.

Senior citizens and Republicans are traditionally the most likely to return their ballots the earliest, whereas younger and more independent voters typically wait until the last week, or even day, to participate.

"The blue wave is still possible to happen," Bentz concedes. "We just sort of expected to see signs of it in the first set of returns."

McDonald sees better signs for Democrats elsewhere, particularly in Georgia, where Democrat Stacey Abrams is vying with Republican Brian Kemp to become the first female African-American governor in the country. Because there's no party registration in the Peach State, a more telling indicator is to examine ballot returns by race.

And the early statistics show African-Americans are returning ballots at a higher rate than 2014; they already make up 30 percent of the vote. White turnout is also up in Georgia, although not as dramatically.

One Georgia voter, James Moy, live-streamed his two-hour journey over a mountain in Costa Rica to mail his absentee ballot. "The reason I'm doing this is because if you're on the fence about voting on the day of because it's, like, a little inconvenient and you don't feel like driving to the polling location, just think about the fact that I'm walking two hours from the rainforest to the post office," Moy says.

In Tennessee, where early voting is approaching presidential-level turnout at more than 400,000 ballots returned, the numbers could bode well for the chances of Phil Bredesen, the Democratic nominee waging an underdog campaign for U.S. Senate.

Democrats usually suffer in midterm elections because many of their most crucial constituencies, like young voters, decline to participate. A higher turnout in Tennessee doesn't mean success for Bredesen, but a lower overall turnout would likely doom his campaign.

Florida Democrats were happy to simply celebrate a smaller GOP early ballot lead. While Democratic ballots still trail Republicans by about 6 percentage points, their deficit was 14 points at this same juncture in the 2014 midterms. Highly competitive races for governor and U.S. Senate are likely to produce high turnout in the Sunshine State, though ballots in pockets of the Panhandle are expected to lag due to the continued recovery from Hurricane Michael's aftermath.

On the other hand, the early returns in Nevada show a narrow statewide lead for Democrats, but longtime journalist Jon Ralston cautioned that it was still unclear if "the wave is blue or purple – or if there will be a wave at all."

But even with all the indications that voters are excited to participate, over-prognosticating which party or candidate will benefit is risky and foolish.

Remember 2016?

Democrats expressed optimism as droves of Latinos flooded polling places in Florida and a surge of unaffiliated white women cast ballots in North Carolina. Journalists evaluated the record-breaking early voting and prescribed "a potentially worrisome sign for Trump."

Trump won both states and the rest is history.

Early voting demonstrates engagement and enthusiasm. It does not foretell who someone is voting for. A registered Democrat standing in a long line may be there to cast a ballot for a Republican; or vice versa.

And perhaps most importantly, a voter doesn't get extra credit for voting early.