As part of its chairman’s desire to close its primaries to all but registered Republican voters, the Colorado Republican Party filed a lawsuit against the Secretary of State Jena Griswold in federal court Monday, seeking to invalidate a ballot measure passed by voters in 2016. The suit, filed on behalf of the party by the attorney who represented Donald Trump after his 2020 election loss, is the latest effort by some Colorado Republicans to push back against Proposition 108, which allows unaffiliated voters to participate in parties’ primary elections and help select general election candidates.