Gia Arnold was arrested after an AR-15, a handgun, a combat knife, and a black ski mask were found in her car when she was pulled over in Niagara Falls, local news station WKBW reported.
Arnold, a mother of three, was charged with criminal possession of an assault weapon. Halim Johnson, 18, was also arrested on gun charges. His connection to Arnold wasn't immediately clear.
Supporters had already launched a legal defense fund for Arnold, which had raised $1,900 by Friday afternoon.
"On Feb 10th Gia Arnold and her boyfriend became victims of the NYS (UN)Safe Act and racial profiling," the fundraising page read. "We are asking all patriots to Rally behind her and help her get out of this horrid mess."
Arnold, then 24, ran as a Republican with strong Tea Party backing in the 2014 62nd District New York Senate race. But she suspended her campaign after making public that she had an extramarital affair just two weeks earlier.
"I had an affair on August 1st and four days later I left my husband," she said about the decision to halt campaigning.
Arnold later jumped back in the race, saying she received an outpouring of support from constituents, but was handily defeated in the race.