Republicans filed a lawsuit in U.S. District Court for the District of Colorado against Secretary of State Jena Griswold, challenging a 2016 voter-approved ballot measure that allows unaffiliated voters to participate in primaries.

The lawsuit was authorized by the state GOP central committee last September, after turning down a request to call off the 2022 primaries.

The suit challenges the 2016 ballot measure as a violation of the Republican Party’s First Amendment rights of free speech and free association, and the 14th Amendment right to equal protection under the law, according to a statement Tuesday from People for Association Rights and Bi-Partisan Limited Elections, a new group that is among the plaintiffs.

The group also asked for a preliminary injunction to block the law for the June 28 primary.

Represented by attorneys Randy Corporon and John Eastman, formerly a professor of conservative thought at the University of Colorado, the plaintiffs include Rep. Ron Hanks of Cañon City, who is seeking the Republican nomination for U.S. Senate; Laurel Imer of Jefferson County, who is seeking the Republican nomination for Congressional District 7; former state Rep. Joann Windholz, chair of the Adams County Republican Party; Dave Peters, who chairs the La Plata County Republican Party and the Congressional District 3 Republican Party; and Casper Stockham, a candidate for CD 7 in 2020.

The plaintiff’s case is funded with donations to the Claremont Institute, a California-based conservative think tank associated with Eastman.

Eastman was banned from speaking at CU over his participation in the Jan. 6, 2021 rally at the U.S. Capitol. A violent mob later attacked the U.S. Capitol to stop Congress from certifying the result of the 2020 presidential election. A report by the U.S. Senate said seven people died in connection with the Jan. 6 attack.

Voters approved Proposition 108 by a 53% to 46% margin. It was backed by Kelly Brough and Joe Black, both leaders with the Denver Metro Chamber of Commerce. Let Colorado Vote, an issue committee, spent $6 million to win voter approval. The initiative’s biggest donor was Kent Thiry, who kicked in $3.1 million. The measure had little opposition, as demonstrated by the $71,000 spent against it.

In their suit, the plaintiffs pointed out that, as of Feb. 1, 2020, there are 954,102 registered active Republican voters, 1,070,804 registered active Democrat voters, and 1,637,864 active unaffiliated voters in Colorado. They said this leads to the “real possibility that unaffiliated voters voting in the Republican or Democrat primary elections would hand the nomination to someone who did not receive a majority or even plurality of votes from Republican or Democrat Party members, thereby placing the party’s imprimatur on a candidate without majority or even plurality support from the party’s members.”

Unaffiliated voters have been encouraged to vote in Republican primaries to defeat candidates preferred by Republican Party voters, such as U.S. Rep. Lauren Boebert in the 3rd Congressional District, the lawsuit said.

In order for the Republican Party to opt out of the primary, it would take three quarters, or a super majority, of the voting members of the central committee, and that threshold has not been met in 2017, 2019 or 2021, the lawsuit said. That places an undue burden on the party to determine for itself the method of choosing its nominees, the lawsuit added.

The plaintiffs are seeking a quick turnaround on the lawsuit, but U.S. District Court Judge Phillip Brimmer, in an order issued Tuesday, said the plaintiffs created their current exigency. He did, however, find the expedited briefing schedule proposed by the plaintiffs reasonable, ordering Griswold to respond by March 14 and the plaintiffs with a reply to that motion by March 21.

The state’s three-page response said the plaintiffs fail to explain why they waited until Feb. 24 to challenge the 2016 law, thereby giving Griswold “mere days notice” to mount a defense.

“Poor planning on [plaintiffs’] part does not translate into a crisis for everyone else,” the state’s response said.

A preliminary injunction hearing is scheduled for March 18.