Alice Kryzan defeated two better-known and better-financed candidates in the 26th District, The Buffalo News reported. She won 42 percent of the vote, while Jonathan Powers, a veteran of Iraq, picked up 36 percent and millionaire Jack Davis 23 percent.
The newspaper said 99 percent of the vote was in from six of the seven counties in the district.
"I feel like the little engine who could," Kryzan told supporters as she claimed victory. "I believed I had a message that was resonating with voters, and the proof of the pudding was what happened today."
Powers received support from the Democratic Congressional Campaign Committee. Davis financed his own campaign, his fourth for the seat.
Democratic leaders have hopes of picking up the seat, because incumbent Republican Thomas Reynolds is retiring, The Hill reported. Chris Lee, the Republican nominee, had no primary opposition.
But Powers will be on the ballot as the candidate of the Working Families Party, which could cut into the Democratic vote.