Mr. Selvaggio runs a company called Direct Action Partners, based in Oregon, that works on progressive campaigns, handling signature gathering and direct action marketing. His company has worked in Oregon, California and Missouri, among other places.

Colorado Rising had hired Mr. Selvaggio to help gather the 98,000 signatures needed to get the measure on the ballot by August 6. But in recent weeks he had argued with the group over the terms of their agreement, according to the lawsuit.

In mid-July, amid the dispute, Mr. Selvaggio packed up boxes of signatures and left the state, according to the lawsuit. Colorado Rising estimates he took about 15,000 signatures.

Mr. Selvaggio did not answer phone calls or an email and his location is unknown.

The lawsuit, which was filed late Wednesday, alleges that Mr. Selvaggio admitted on July 20 to shipping the signatures out of state. Emails indicate that Mr. Selvaggio reached out to election officials three days later to see if it was legal to review them outside of Colorado.

“There is no prohibition that I am aware of that prohibits you from doing so,” an official from the secretary of state’s office said, responding to the question of whether it was legal to remove the signatures.

But in at least one conversation with Colorado Rising, according to members of the group, Mr. Selvaggio said that he had been approached by the industry-funded group aimed at killing the initiative.

Pac/West, a communications company organizing the fight against the measure, had come to him and asked him to throw the campaign, he told Ms. Spiegel and at least one other organizer, Lauren Petrie.