DENVER — Former Colorado governor John Hickenlooper, a candidate for U.S. Senate, violated state law in 2018 when he accepted a ride in a Maserati limousine at a conference in Italy and traveled on a private jet owned by a home builder to Connecticut for the commissioning of the USS Colorado submarine, a state ethics commission found Friday.

The Independent Ethics Commission found the Democrat violated a state constitutional gift ban, known as Amendment 41, for public officials approved by Colorado voters in 2006. The measure led to the creation of the ethics commission.

“If we allow this kind of private travel, it accentuates the cynicism that led to Amendment 41,” said Commissioner Bill Leone, a former U.S. attorney whom Hickenlooper first appointed to the panel in 2013.

The panel’s finding is likely to be a political headache for Democrats who see the former two-term governor and onetime Denver mayor as their best candidate in their bid to flip a Republican-controlled Senate seat and reclaim the majority.

Hickenlooper is just weeks away from a June 30 primary against Andrew Romanoff, a former Colorado House speaker. The winner will challenge Republican Sen. Cory Gardner, considered among the most vulnerable incumbents, in the November election. Hillary Clinton won Colorado and Maine in 2016 — two Democratic-leaning states with competitive Senate races.

The five-member panel cleared Hickenlooper, who briefly ran for president last year, of four other counts alleged in a complaint filed in 2018 by the conservative Public Trust Institute. These included flights on company planes owned by friends.

Former state Republican House speaker Frank McNulty filed the document, which alleged that the governor “repeatedly traveled on private airplanes owned by corporations and accepted travel expenses paid for by corporations” in direct violation of the state constitution.

The ruling Friday evening followed a dramatic week in which Hickenlooper refused to testify at a Thursday hearing and the commission found him in contempt for refusing to comply with a subpoena. At the Friday hearing, his attorney acknowledged that the proceedings, and Hickenlooper’s initial refusal to appear before the committee, will become a part of the Senate race.

“My guess is we will be living with this in the political discourse for weeks or months,” said Mark Grueskin, a lawyer for Hickenlooper.

The commission will debate potential sanctions for the ethics violations and the contempt charge on June 12.

On Friday, President Trump tweeted: “Democrat John Hickenlooper Held in Contempt After Failing to Comply with Subpoena over Ethics Complaint. Got caught big time with his hand in the cookie jar. Should be the end of his Colorado Senate bid. Makes no difference, we already have a GREAT Senator!”

After the commission’s decision, Joanna Rodriguez, a spokeswoman for the National Republican Senatorial Committee, accused Hickenlooper of a “serious disregard for Colorado’s ethics laws.”

“He is guilty of shrugging off the state’s ethics rules and violating the trust taxpayers had placed in him as governor,” she said.

Melissa Miller, a Hickenlooper campaign spokesman, said in a statement: “We fully expect the special interests who’ve exploited this process to continue to mislead Coloradans with negative attacks because they know John Hickenlooper will be an independent voice in the U.S. Senate.”