Federal judge rules Colorado GOP primary law unconstitutional

Ruling strikes down high threshold for closing primaries to unaffiliated voters

Apr. 1, 2026 at 4:38pm

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A federal judge has struck down a key part of a 2016 Colorado ballot initiative that set a high three-fourths threshold for political parties to close their primary elections to unaffiliated voters. The judge ruled that the provision violates the First Amendment's protections of freedom of association.

Why it matters

The ruling is a victory for the Colorado Republican Party, which had argued the high threshold made it too difficult to close primaries and protect GOP candidates. It could impact future primary elections in the state, where unaffiliated voters have come to make up a growing share of the electorate.

The details

The law previously said that if a political party wanted to close its primary so that only its own registered voters could participate, three-quarters of that party's central committee must vote in support of the change. Judge Philip A. Brimmer ruled that this threshold was unconstitutionally high, calling it 'more akin to a hurdle to amend a foundational governing document, such as the United States Constitution, than a traditional means of regulating political parties.'

  • The Colorado GOP filed the lawsuit against the Secretary of State's Office in 2023.
  • Brimmer previously rejected the GOP's request to immediately close primaries to unaffiliated voters in 2024.
  • The lawsuit dragged on for two years before the judge issued his ruling.

The players

Judge Philip A. Brimmer

A federal judge based in Denver who ruled that the Colorado law's high threshold for closing primaries to unaffiliated voters is unconstitutional.

Colorado Republican Party

The state GOP filed the lawsuit against the Colorado Secretary of State's Office, arguing the high threshold made it too difficult to close primaries and protect Republican candidates.

Dave Williams

A conservative hardliner who had blasted the 2016 ballot initiative as a 'radical leftwing' effort and argued that closing the primaries was vital to protecting true Republican candidates.

Brita Horn

The current chair of the Colorado Republican Party, who is stepping down later this month.

Jena Griswold

The Colorado Secretary of State whose office was named in the GOP's lawsuit.

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What they’re saying

“'The background and origin of the three-fourths opt-out provision is unclear. What is clear is that it constitutes an unusual and difficult barrier for the central committee to overcome, more akin to a hurdle to amend a foundational governing document, such as the United States Constitution, than a traditional means of regulating political parties.'”

— Judge Philip A. Brimmer, Federal Judge

What’s next

The state GOP meets on April 11 for its state assembly, where it will nominate some candidates for this year's June 30 primaries. The ruling would apply to both the Republican and Democratic parties, should Democrats later choose to close their primaries as well.

The takeaway

This ruling is a victory for the Colorado Republican Party, which had argued the high threshold to close primaries made it too difficult to protect GOP candidates. It could have significant implications for future primary elections in the state, where unaffiliated voters have become an increasingly large share of the electorate.