Voters went to the polls across the country at the highest rate for a midterm election in more than 50 years on Tuesday, and Colorado retained its status as one of the highest-turnout states.

Though counting still was under way in several Colorado counties Wednesday — with more than 400,000 ballots still out — the state was in the top five nationally, according to the United States Elections Project. Americans cast an estimated 113 million ballots in the election, the group said.

Colorado’s turnout exceeded the state’s last several midterm elections, going back at least to 2002, according to data from the Secretary of State’s Office.

The high turnout was driven by unaffiliated voters, who turned in slightly more ballots than either Democrats or Republicans. While Democrats and unaffiliated voters turned out in much larger numbers than in 2014, ballot returns from GOP voters increased only slightly, while women outpaced men by more than 100,000 ballots.

Younger voters showed up at a much higher rate than usual for a midterm.

Colorado Election Results

“We basically had presidential turnout yesterday for (a) mid-term election,” Republican pollster David Flaherty tweeted, referring to a party breakdown that was split into near-equal thirds among Democrats, Republicans and unaffiliateds, who leaned left.

The result was a Democratic sweep of state offices, including Jared Polis’ election as governor and the party’s retaking of the state Senate’s majority.

How did Colorado’s turnout compare?

By the Elections Project’s projection, nearly 60 percent of eligible voting-age adults in Colorado participated in Tuesday’s election, compared to 48 percent nationally. The national rate was the highest participation since the 1966 midterm, according to Michael McDonald, an associate professor of political science at the University of Florida who runs the project. (See an updated look at voter turnout here.)

McDonald’s figure takes into account all adults who could register to vote.

Colorado’s county clerks sent 3.2 million mail ballots to everyone listed as an “active voter,” based on voting history in recent election cycles. The Secretary of State’s Office said in its latest ballot-return report Wednesday afternoon that 2,518,280 ballots had been returned, or 78 percent of the total mailed.

While high for a midterm election, that trails the 86 percent active-voter turnout in the 2016 presidential election.

Another way to calculate turnout is to compare ballot returns to voter registration, which totals 3.9 million including “inactive” voters who didn’t automatically receive a mail ballot. The mail-ballot return figure reflects 64 percent turnout among registered voters.

By whichever measure, Colorado’s turnout rates are considered high, especially for a midterm election. In McDonald’s projections, Colorado was behind only Minnesota, Michigan, Wisconsin and Oregon, though the turnout projections were still in flux.

Hundreds of thousands of votes are still out

In Colorado there still were a lot of votes to be counted as of Wednesday afternoon.

The state said 2.5 million ballots have been returned, and election results reflected slightly more than 2.1 million ballots counted as of 5 p.m. That means roughly 400,000 still were being processed by counties.

The largest chunk of those were in Denver, where Denver Elections Division spokesman Alton Dillard estimated Wednesday that more than 100,000 ballots remained to be counted.

Arapahoe, Jefferson, Weld, Pueblo and Boulder counties were also among those still processing ballots Wednesday.

Denver expected the counting of its ballots to last through Thursday or Friday, Dillard said.

Both Denver and Boulder typically see higher Election Day turnout than suburban and rural counties, prolonging their counts. An added complication this time, at least in Denver’s case, was that its six-page ballot required three cards, one more than usual. That means, Dillard said, that each ballot takes longer to process and count.

Turnout in the governor’s race

In Colorado’s marquee governor’s race, Polis, a Democratic congressman, defeated state Treasurer Walker Stapleton. Polis was leading 53 percent to 43 percent as of Nov. 13.

County-by-county results show that Stapleton performed well in traditional Republican strongholds, including El Paso, Douglas, Weld and Mesa Counties. But his strongest margins came on the Eastern Plains and in a few other sparsely populated rural counties.

Polis, meanwhile, dominated in the usual Democratic strongholds, including Denver, Boulder and mountain resort communities, while building up a firewall in suburban Jefferson, Adams and Arapahoe counties, traditional swing areas where returns showed him with double-digit leads.

Here is a look at how the candidates did in each county (click here to open in a new window):