Driven by fears of extremism and worries about what they see as an authoritarianism embodied in Ms. Boebert, thousands of Democrats in the sprawling third congressional district of Colorado have rushed to shore up her Republican challenger, State Senator Don Coram. Their aim is not to do what is best for Democrats but to do what they think is best for democracy…

[A]s Mr. Arndt noted, anti-Trump Republicans have put aside stark differences with liberal policies and voted for Democrats since 2016. It is time, he said, that Democrats return the favor and put preservation of democracy above all other causes…

A nascent infrastructure is supporting the trend. The Country First Political Action Committee, established by Representative Adam Kinzinger, an anti-Trump Republican from Illinois, has used text messages and online advertising to rally opposition against what the congressman has called the most “toxic” and partisan Republicans. Those include Representatives Madison Cawthorn, Republican of North Carolina, and Jody Hice, Republican of Georgia, who, with Donald J. Trump’s backing, tried to defeat Georgia’s secretary of state, Brad Raffensperger, after he resisted Mr. Trump’s push to “find” the votes to nullify President Biden’s victory there…

In Colorado, voters can cast ballots in the Republican primary if they are registered with the party or as unaffiliated. In Ms. Boebert’s district, Democratic Party officials have tallied about 3,700 more unaffiliated voters in this year’s Republican primary compared with two years ago. They are largely concentrated in the Democratic hubs of Pitkin County, home of Aspen, where one can never be too rich or too liberal, and LaPlata County, where Durango is filling with young people.