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DENVER — Mario Nicolais, a Republican attorney who led a group of conservatives that advocated for the passage of civil unions legislation, announced over the weekend that he’s running for a state senate seat.

Nicolais, an attorney at the Hackstaff Law Group, plans to challenge Democratic Sen. Andy Kerr in District 22, which includes parts of Lakewood and south Jefferson County.

“The current legislature has failed Colorado, and Andy Kerr has failed the residents of Jefferson County with his blind adherence to a political agenda,” Nicolais said.

“Jefferson County deserves an independent-minded Senator who is committed to protecting individual rights, limiting the size and scope of government, and empowering our communities.”

Kerr, a school teacher who won a close race for his senate seat last year over former GOP state Rep. Ken Summers, was a swing vote who helped Democrats pass a number of controversial gun control measures earlier this year.

A Denver resident, David Cassidy, was even arrested for threatening to remove Kerr from office, “either by ballots or by bullets.”

In a press release announcing his candidacy, Nicolais also blasted Kerr for supporting a major Democratic elections overhaul that will mail a ballot to every registered voter and let voters register as late as Election Day.

As an attorney at Hackstaff, Secretary of State Scott Gessler’s former firm, Nicolais has been involved with several cases related to Colorado elections law.

He also served on the state’s Reapportionment Commission, which re-drew all 100 state House and Senate districts last year.

And, in 2012, he formed the group, Coloradans for Freedom, uniting conservatives who supported civil unions legislation based on a belief in personal freedom and limited government.

When House Republicans blew up the entire calendar at the end of the 2012 session in order to prevent a vote on civil unions, Nicolais offered a memorable and ultimately accurate lament: “Civil unions will pass,” he said.

“And so too will the Republican House majority.”

“It’s going to be interesting to see where the gay mafia lands on this one,” one Capitol observer told FOX31 Denver.

Kerr, too, has long been a steadfast supporter of LGBT rights; gay politicos flocked to his side in 2012 when Brian Carroll, an openly gay military veteran, announced he was considering a primary challenge against Kerr.

Republicans need to gain three seats in 2014 to win back a Senate majority; Nicolais’s candidacy could make the S.D. 22 race the most competitive and expensive in the state.

Kerr noted that he and Nicolais both graduated from Green Mountain High School, but that the similarities between them end there.

“Mr. Nicolais getting into the race is a tribute to the great social studies teachers at our alma mater,” Kerr told FOX31 Denver. “Of course, since then he’s been involved in partisan politics while I’ve been working to create jobs and bring our community together.”