Unaffiliated voters now make up more than half of Colorado’s registered electorate, and for the first time, more primary ballots are going to voters without a party affiliation than to registered Democrats or Republicans.

Colorado began allowing unaffiliated voters to participate in primary elections in 2018, following voters’ approval of Proposition 1088 in 2016.

This year’s June primary is the first in which both major parties have contested statewide races, with at least two candidates running for major races such as governor and attorney general in each party.

Given that shift, unaffiliated voters — including those who recently left a party and those who have long identified as independents — could play a significant role in determining which candidates advance to the November general election.

Who are Colorado’s unaffiliated voters?

More than two million Colorado voters are registered as unaffiliated, and while they don’t vote as a single bloc, political scientists say some patterns are emerging within this fast‑growing group. Ryan Strickler, a political-science professor at Colorado State University Pueblo, notes that researchers have begun to identify trends among these voters.

“The unaffiliated are going to be a little more moderate; they tend to follow politics a little less, and they tend to be less politically-engaged than registered Democrats or registered Republicans,” he said, adding that the lack of political engagement may give candidates with higher name recognition an advantage.

Data show a national shift away from the two major parties, with a recent Gallup poll finding that 45% of Americans now identify as independents.

In the 2024 election, nearly 1.5 million unaffiliated voters turned in ballots in Colorado, compared to 900,000 Democrats and about 830,000 Republicans.

However, turnout in primary elections is much lower. In 2024, only about a quarter of Colorado voters cast ballots in the state primary election, with unaffiliated voters accounting for about 36% of the total turnout.

Colorado’s unaffiliated voters generally lean Democratic, but many hold more traditionally Republican views on issues such as immigration, public safety and the Taxpayer’s Bill of Rights, said Beth Hendricks of the League of Women Voters.

“While our unaffiliated voters do tend to lean Democratic, they have been playing their hand in the Republican primaries and it seems that they’re looking to kind of keep things a bit more balanced and less extreme,” she said.

For the most part, Strickler said, the majority of unaffiliated voters choose candidates from the same party election after election.

“It’s not like every one of these unaffiliated voters is uber-moderate and could go either way,” he said. “I think many of them are gonna solidly vote Democrat or Republican in November, no matter what.”

Targeting unaffiliated voters

More than two million additional potential voters are participating in this year’s primary, forcing candidates to broaden their messaging to appeal not just to their party’s base but also to unaffiliated and undecided voters.

However, Hendricks admitted, it may take some time for candidates to develop that strategy — if they choose to at all.

She said candidates now have to reach roughly three‑quarters of Colorado voters rather than just their party faithful, yet many still focus on attacking the opposition instead of speaking to unaffiliated voters, who tend to be deeply skeptical of both parties.

“I personally think that candidates need to really think about that and start changing up their rhetoric to appeal to more people rather than just bashing the other party,” Hendricks added.

Some candidates don’t want unaffiliated voters participating in their primaries at all; state Rep. Scott Bottoms, now running for governor, joined an unsuccessful push to bar unaffiliated voters from the GOP primary, arguing that Colorado’s semiopen system is unconstitutional because it requires Republicans to let nonmembers help choose their nominees.

Unaffiliated voters can pose a unique opportunity for candidates, particularly those from a more moderate wing of their respective parties, Strickler said.

State Sen. Barbara Kirkmeyer and U.S. Sen. Michael Bennet are generally considered the “moderate” candidates in their respective gubernatorial primaries, though, of course, that term is subjective.

“For Barbara Kirkmeyer on the Republican side or Michael Bennet on the Democratic side, maybe part of their strategy is trying to appeal to these otherwise not engaged voters with more of a moderate message or Bennet utilizing his name recognition, things like that,” Strickler said.

Seth Masket, a political-science professor at the University of Denver, said unaffiliated voters tend to vote for what they know, whether it’s an incumbent or a candidate with an extensive advertising budget.

“If someone has a much bigger advertising spending budget, they’re more likely to see that person’s ads or signs or radio broadcasts, so they’re more likely to decide late and be influenced by campaign things,” he said.

While Masket said unaffiliated voters and voters in general dislike attack ads, research shows that their messaging can be effective.

“Unaffiliated voters are really bothered by attack ads, and that is part of the reason they don’t want to be part of a party, but that doesn’t necessarily mean it causes them not to vote,” he said. “My impression is they actually do pay some attention to those ads and they do use the information in those ads to cast a vote, even if they’re annoyed by them.”

Those attack ads are primarily geared toward registered party members, however, said Strickler.

He said that even with a large pool of unaffiliated voters in play, campaigns still have to energize their core partisans, who remain the most dependable primary voters — which helps explain the steady stream of negative ads.

Those attacks, Strickler noted, can be highly motivating for the base, but they also risk turning off unaffiliated voters who may already feel disillusioned with both parties, suggesting campaigns may be overlooking something by leaning so heavily on negativity.

Another popular campaign strategy is what Strickler calls “values-based” or “character-based” messaging.

Strickler noted examples like U.S. Sen. John Hickenlooper’s “This is Me” ad, filmed as he walks through the woods and Phil Weiser talking about his mother’s birth in a World War II concentration camp — reminders that unaffiliated voters, who tend to be less politically engaged, may weigh a candidate’s personal story, values or background when deciding how to vote.

Strickler pointed to U.S. Sen. John Hickenlooper walking through the forest in his recent “This is Me” ad or Phil Weiser talking about how his mother was born in a concentration camp during World War II. Because unaffiliated voters tend to be less politically involved, they may base their vote, at least in part, on a candidate’s story, personal values or background.

What’s next?

As dissatisfaction with both major parties continues to grow, experts anticipate an increasing share of Coloradans will register as independents in the coming elections.

“It’s a sea change,” said Hendricks. “For almost 250 years, we’ve been operating in this one way, so it’s a lot to move away from that, but it’s happening and candidates need to recognize that.”

In Colorado, residents who don’t select a party affiliation when they obtain a driver’s license or state ID are automatically registered as unaffiliated voters.

The primary election is June 30.