One in three Colorado voters are not affiliated with any party. In fact, “unaffiliated voters” make up the largest single group of voters in the state.

But only those who are registered with a major party could participate in last week’s primary election.

Still, the Secretary of State allows for unaffiliated voters to change party affiliation at any time, including the day of the primary – and data suggests that they did.

In June, nearly 17,000 unaffiliated voters apparently joined one of the two major parties, presumably in order to participate in primary elections throughout the state. In addition, about 24,000 more people also registered to vote last month – bringing the total of active, registered voters in the state to more than 3,015,000.

Statewide, the Democratic Party gained 22,442 voters while Republicans gained 16,893.

But in spite of these increases in registration, just 20 percent of active registered voters actually voted in US Senate primary.

In Denver, turnout was higher. At least 30 percent of active Democratic voters participated in the race for the District Attorney. Beth McCann won by a margin of 9,000 votes. There is no Republican challenger, but chief deputy DA Helen Morgan is running as an independent.

According to data collected by the Colorado Secretary of State, unaffiliated voters still account for the largest demographic of active registered voters in the state, even after thousands became affiliated.