Doug Robinson, a first-time candidate and nephew of Mitt Romney, is demanding the secretary of state’s office conduct a formal investigation after a secretly recorded phone call raised questions about one person circulating petitions for Stapleton, the current state treasurer.

“We spent so much time and money trying to do this the right way it makes me upset that people were doing it the wrong way,” Robinson said in an interview after claiming Stapleton’s petitions were “gathered illegally.”

The extraordinary move comes as Robinson struggles to gain traction in a crowded field in which Stapleton tops the early polls and fundraising reports. The dispute echos concerns from 2016, when forged voter signatures marred the Republican primary for U.S. Senate — a move that contributed to the party’s loss in November.

Stapleton’s campaign and the firm it hired to collect voter signatures, Kennedy Enterprises, deny any wrongdoing. “The entire Walker Stapleton signature campaign was performed lawfully,” said Dan Kennedy in a statement.

The state is currently reviewing Stapleton’s petitions to see whether he collected the requisite 1,500 in each of Colorado’s seven congressional districts to earn a place on the ballot. Robinson also submitted signatures to qualify, and his status remains undetermined.

The firm hired by the Robinson campaign to solicit signatures filed a complaint Feb. 23 with the secretary of state’s office that alleged a petition circulator working on Stapleton’s behalf told them he was not registered to vote in Colorado and did not certify that he collected the signatures — factors that could render them invalid and may have violated state law.

The firm’s founder, Dustin Olson, later secretly record a phone call with the same person, identified as Daniel Alejandro Velasquez, under the pretense that he may hire him to do work. The call, first reported by Denver7, takes place as Velasquez is heard soliciting voters to collect signatures.

Stapleton’s campaign and Kennedy Enterprises said they have no record of Velasquez circulating petitions.

The secretary of state’s office tried to reach him but was unsuccessful. Ben Schler, the office’s operations and legal manager who conducted the initial inquiry, said the audio concerns him, but he does not have enough evidence to determine if Velasquez — or anyone else — violated the law.

“To hear a conversation like that — that was fairly long and detailed — is definitely troubling,” he said in an interview. “I just think from an evidentiary perspective there’s a difference between something that is troubling and something that we can take action on.”

Robinson’s complaint about another Stapleton petition collector was dismissed because the voter registration was verified.

Stapleton spokesman Michael Fortney, whose firm also consults for Secretary of State Wayne Williams’ re-election campaign, said in a statement that he takes the claim seriously but he suggested the motivation for the complaint was political.

The secretary of state’s office said Robinson could take the matter to the local district attorney. His campaign said it wants the secretary of state’s investigation to continue.

“We think there is something there,” Robinson said. “And we think they should look into it.”