Alaska retired teacher Dan J. Sullivan, a Republican running against incumbent Sen. Dan Sullivan, colluded with a liberal group to run attack ads against the senator, Americans for Public Trust alleges. 

Democratic strategist Amber Lee, who worked for Dan J. Sullivan's campaign while sitting on the board of the left-leaning 907 Initiative, which is a government transparency group that spent approximately $1.5 million on ads attacking the incumbent, the New York Post reported. 

Caitlin Sutherland, the executive director of watchdog group Americans for Public Trust, which filed the complaint with the Federal Election Commission Tuesday, told the Post that it's a violation of federal election law to work for both Dan J. Sullivan's campaign and an outside group that's spending millions on advertisements benefiting the campaign. 

About $575,000 of 907 Initiative’s spending against Sen. Sullivan took place during the final 90 days of the primary race, Americans for Public Trust alleged in their complaint. 

Just one day after Dan J. Sullivan filed to run, the 907 Initiative attacked Sen. Sullivan with an ad titled "Stop Raising Costs." 

The retired teacher's campaign owed Amber Lee Strategies $4,380.41, the complaint noted.

Dan J. Sullivan, who has been called "Decoy Dan," entered the race in May, and his candidacy faced accusations of being an attempt to confuse the ballot with the same name as the incumbent. After a legal fight over whether he was a “good faith” candidate, Alaska courts kept him on the ballot.

Also in the race for the U.S. Senate are Democrat Mary Peltola and Republican Gerald Heikes.