Despite the improved chances for a Republican takeover of the House, some unions are spending against Democratic incumbents who voted "no" on healthcare reform.

Unions vowed to go after members who didn't support the bill, and some are keeping that pledge.

The Service Employees International Union (SEIU), for instance, has spent almost $300,000 on direct mail and other activities in support of union activist Mac D'Alessandro's primary challenge to Rep. Stephen Lynch (D-Mass.).

D'Alessandro and SEIU officials say he wasn't recruited to run because of Lynch's vote against the healthcare reform bill in March, but it's been the main issue of his candidacy.

"I made a decision on my own, and what I like to say is that the only person who asked me to get into this race was Steve Lynch," D'Alessandro told The Ballot Box.

He said healthcare wasn't the only reason he decided to run but rather, it was the "final straw."

"It goes all the way back to his vote to authorize the war in Iraq and its continued funding time and time again, even as our economy here at home fell apart," he said, also citing Lynch's anti-abortion position.

Lynch wasn't without union support — he was endorsed by the AFL-CIO during the primary, but the union didn't make any independent expenditures on his behalf.

D'Alessandro maintains that support for Lynch among "working families" has dropped since he voted against healthcare reform.

"I've canvassed and door-knocked and talked to small-business owners in every city and town in this district and there is a lot of frustration with Congressman Lynch’s vote on healthcare reform," he said. "A lot of it."

"I think that his 'no' vote on healthcare was a vote against the interests of middle income families, middle-class families, working families, not to mention small businesses," he said. "Those are reforms that benefit a lot of working families in this district."

Lynch's campaign says concerns about government spending and the deficit are what the congressman hears about from his constituents.

"When Steve knocks on doors he hears concerns about the healthcare reform bill and the Wall Street bailout, and the concern is with the positions Mac holds on both of those bills," said Scott Ferson, a spokesman for Lynch's campaign.

Ferson suggested D'Alessandro had been knocking on doors in Somerville and Cambridge, which are in the more liberal 8th district. "Thank God we're running in the 9th," Ferson said.

The Massachusetts primary vote is Tuesday.