The primary election that took place in Colorado Tuesday was special for two reasons: It saw the highest voter turnout in state history, and was the first primary since 1998 to feature contested races for governor from both major parties.

In voter turnout, the election blew by the previous record holder.

In 2010, the previous highest-turnout primary yielded 774,071 ballots cast. On Tuesday, county clerks around the state counted 1,172,780 Coloradans had voted, according to statistics provided Wednesday afternoon by the Colorado Secretary of State’s Office.

There are about 3.2 million active registered voters statewide.

Of that number, Democrats cast 467,924 ballots, Republicans cast 414,217 and, for the first time, unaffiliated voters cast 290,639.

The Secretary of State’s Office said 13,546 voters voted in person, either via a machine or paper ballot: 9,647 voted in the Democratic races and 3,899 in the Republican races.

Voters likely were drawn to turn out because of the two contested races for governor, but also because both major parties fielded four gubernatorial candidates, said Lynn Bartels, communications director for the Colorado Office of the Secretary of State.

“This shows you what having a really interesting ballot will do,” Bartels said.

Local races for county sheriff and county commissioner also likely led to turnout enthusiasm, she said.

“Even if you didn’t have unaffiliated voters, just the Democrats and Republicans that turned out is more than any previous primary … in the last decade,” Bartels said.

This is the first primary election where unaffiliated voters were allowed to automatically participate.

Some unaffiliated voters indicated a preference for a Republican or Democratic ballot ahead of time and were mailed only that party’s ballot. But, the majority did not express a preference and therefore were sent both ballots, with the caveat: Only vote one, because if you vote both, neither ballot will count.

Data from the Colorado Secretary of State’s Office show few unaffiliated voters ended up failing to follow the rules.

As of late Tuesday, the statewide “spoilage” rate, or the number of unaffiliated ballots rejected due to voting both, was 2.2 percent, or about 5,000 ballots, according to data provided by the Secretary of State’s Office. The number is likely to increase slightly in the following eight days as county clerks across the state continue to count ballots and tally the official results.

Some officials predicted this number could be as high as 7 percent, Bartels said. Beginning in March the office embarked on the UChooseCO campaign to spread the “only vote one ballot” message.

In Larimer County, voters mailed in 79,179 total ballots; 31,190 came from Democrats ballots, 26,409 from Republicans, and 21,580 unaffiliated ballots. Additionally, 956 people voted in person.

In Larimer County, the unaffiliated mail-in ballot spoilage rate was 1.7 percent, or 302 ballots, according to a count from late Tuesday.

Comparatively, in Boulder County the rate was 1.1 percent or 157 ballots, and in Weld County the rate was 3 percent, or 257 ballots, also per late-Tuesday figures.

Statewide, the majority of unaffiliated voters selected to vote in the Democratic races. About 10,000 unaffiliated voters selected ahead of time to receive only the Democratic ballot, and about 5,000 selected to receive only the Republican ballot.

Of those unaffiliated voters statewide who received both ballots, voters chose to fill out the Democratic ballot almost twice as often as they filled the Republican ballot. There are still about 30,000 unaffiliated envelopes to be opened across the state, which will yield more data.

The ballot counts are based on unofficial results.

Official results will be published July 5, and will include ballots still to arrive from military and overseas voters, as well as ballots from voters alerted by mail that they must verify their ballot envelope signatures.

Julia Rentsch: 970-699-5404, jrentsch@reporter-herald.com