Democrats scored an upset in one of New York’s most conservative Congressional districts on Tuesday, dealing a blow to the national Republican Party in a race that largely turned on the party’s plan to overhaul Medicare.
The results set off elation among Democrats and soul-searching among Republicans, who questioned whether they should rethink their party’s commitment to the Medicare plan, which appears to have become a liability heading into the 2012 elections.
Two months ago, the Democrat, Kathy Hochul, was considered an all-but-certain loser in the race against the Republican, Jane Corwin. But Ms. Hochul seized on the Republican’s embrace of the proposal from Representative Paul D. Ryan of Wisconsin, to overhaul Medicare, and she never let up.
On Tuesday, she captured 47 percent of the vote to Ms. Corwin’s 43 percent, according to unofficial results. A Tea Party candidate, Jack Davis, had 9 percent.
Voters, who turned out in strikingly large numbers for a special election, said they trusted Ms. Hochul, the county clerk of Erie County, to protect Medicare.
“I have almost always voted the party line,” said Gloria Bolender, a Republican from Clarence who is caring for her 80-year-old mother. “This is the second time in my life I’ve voted against my party.”
Pat Gillick, a Republican from East Amherst, who also cast a ballot for Ms. Hochul, said, “The privatization of Medicare scares me.”
The district, which stretches from Buffalo to Rochester, has been in Republican hands for four decades, producing influential figures like Representative Jack Kemp and siding with Carl P. Paladino, a Republican, over Andrew M. Cuomo in the governor’s race last year.
The campaign drew intense interest, with both major parties in Washington and their allies flooding the district with radio and television advertising. Total spending exceeded $6 million.
Of course, there are limits to how much broader meaning can be extrapolated from a special election, which can be shaped by local dynamics and personalities.
Still, on Tuesday, Republicans were examining the results and debating how the party lost the seat, despite outspending the Democrats.
Some Republicans suggested that it would be oversimplifying to attribute the results to a single issue, saying that Ms. Corwin proved a less nimble and ultimately less appealing candidate than Ms. Hochul, who campaigned energetically and with great focus. When Medicare erupted in the race, Ms. Corwin, a wealthy former Wall Street analyst, was knocked off balance and struggled to respond.
In the closing hours of the race, Ms. Corwin admitted as much, saying about her rival’s attacks: “When she started making these comments, I thought, ‘This is so outrageous no one would ever believe it.’ Apparently some people did.”
Others cited the presence of the third candidate, Mr. Davis, who ran on the Tea Party line after failing to win the Republican nomination. He not only drew conservative support away from Ms. Corwin, but also turned his aggressive attacks on her in the end, contributing to her high negative numbers.
On the other hand, Ms. Hochul maintained a positive image conveying a homespun quality, speaking with a Buffalo accent, connecting naturally with voters.
In her victory speech Tuesday night, she noted that her mother and father, who have retired to Florida, were making phone calls to voters on her behalf for months.
“I was talking to voters as far away as Dansville, and they said, ‘You know, I was talking to your mother,’ ” she said. “And I know that you don’t say no to my mother.”
Party luminaries like former President Bill Clinton recorded phone calls for Ms. Hochul’s campaign, and on Tuesday evening Ms. Hochul was fielding congratulatory messages from Vice President Joseph R. Biden Jr. and others.
As the clerk of Erie County, she oversees the automobile bureau, which issue driver’s licenses; Ms. Hochul gained prominence in 2008 when she challenged former Gov. Eliot Spitzer’s plan to issue licenses to illegal immigrants.
“I remember when she was in the auto bureau in Buffalo, she did a lot with the license plates,” said Jim Van Wagner, a Republican and former auto worker from Albion, adding, “She’s a good one.”
Still, given the makeup of the district, one of four in the state that John McCain carried in 2008, Republicans said they needed to understand if they had misread the public.
“It’s a Republican district with a solid Republican candidate,” said Representative Peter T. King, a Republican from Long Island. “What went wrong? We definitely have to determine the extent to which the Medicare issue hurt us.”
Ms. Corwin, in her concession speech, said she had not enjoyed the national attention the race had drawn. But she also offered a strong defense of the need for the country to grapple with tough issues, suggesting the Democrats were simply playing crass politics.
“While the pundits and political strategists, many of whom don’t even live here, will talk about what we should or should not have done in this campaign, I just want everyone to know that I confronted the issues head on. That leadership isn’t about ducking from the issues, leadership isn’t about running away from what you believe in.”
She added: “My parents raised me to dig in my heels and fight for what you believe in, to take a stand and to work with others to accomplish great things.
The seat became vacant in February when Representative Christopher Lee, a Republican, abruptly resigned after he e-mailed a shirtless photo of himself to a woman and it was published on the Internet.
Top Republicans, including the House speaker, John A. Boehner of Ohio, and the majority leader, Eric Cantor of Virginia, traveled to the district to provide support to Ms. Corwin. At the same time, the national party and its allies, including the United States Chamber of Commerce and a group tied to the Republican strategist Karl Rove, jumped in, spending at least $1.1 million on radio and television ads supporting Ms. Corwin.
Democrats brought out their heavy hitters, including Representative Nancy Pelosi of California, the House Democratic leader, who sent out fund-raising solicitations casting the race as an opportunity for Democrats to win in the backyard of Republicans.
The race also marked the debut of House Majority PAC, a group recently established by Democratic strategists as a counterbalance to the slew of conservative organizations that helped Republicans make significant gains in the 2010 elections. House Majority PAC spent nearly $400,000 on advertising in the race.