Sink "was ultimately brought down because of her unwavering support for Obamacare, and that should be a loud warning for other Democrats running coast to coast," said Representative Greg Walden, an Oregon Republican and chairman of the National Republican Congressional Committee, which spent at least $2.2 million backing Jolly's attacks on Sink.

Succeeding young

Jolly won in a district represented for four decades by the late Republican Representative C.W. "Bill" Young. When Jolly takes office, Republicans will hold 233 congressional seats to Democrats' 199. There are three vacant seats in the 435-member House. The outcome makes it less probable Democrats will gain back the majority in that chamber.

Jolly, a 41-year-old former lobbyist who raised less than half of Sink's $2.5 million through Feb. 19, got help from outside groups that spent more than $5 million, mostly on ads slamming Sink over her support of Obama's health-care law.

At the end, though, Jolly attempted to portray the contest more as a matter of home-town politics.

"This race is not about defending a broken agenda in Washington or advancing a broken agenda in Washington," Jolly told a room full of supporters in a 12-minute victory speech last night. "This race is about representing Pinellas County."

Sink, in an e-mail to supporters after the contest was called, said: "While tonight was not the result we were hoping for, I am proud of the race we have run and so grateful for the countless Pinellas residents, volunteers and supporters who put their faith in our campaign."

Obamacare factor

The U.S. Chamber of Commerce's political committee spent at least $1.2 million on television and online ads that touted Jolly and attacked Sink over Obamacare.

"Canceled health plans, higher premiums, Medicare cuts, people losing their doctors," the narrator of one Chamber ad said. "A disaster for families and seniors. With Alex Sink, the priority is Obamacare, not us."

This was among the ads running as often as about 275 times daily in the district, with outside groups like the Democratic Congressional Campaign Committee and the National Republican Congressional Committee testing which kinds of messages might work best with persuadable voters.

The ads aired throughout the Tampa Bay media market, home to one out of every four registered voters in Florida, said Susan MacManus, who teaches political science at the University of South Florida in Tampa. Ads ran more than 1,900 times in the final seven days before the election, according to New York- based Kantar Media's CMAG, which tracks advertising.

Message test

"The campaigns and the parties and consultants are going to be testing how well the messages resonated with this particular market," MacManus said. "I'm expecting that the post-analysis will be a careful focus-group-type look at how the ads played."

Groups aiding Jolly spent at least $5 million and groups favoring Sink spent at least $3.8 million, according to the Washington-based Center for Responsive Politics.

Democratic National Committee Chairwoman Debbie Wasserman Schultz, a House member from Southeast Florida, attributed the loss to "Republican special interest groups" pouring millions of dollars into a district the party has held for 60 years.

"The agenda they are offering voters has a singular focus – that a majority of voters oppose – repealing the Affordable Care Act that would return us to the same old broken health care system," she said in a statement last night.

Beachside District

Sink, 65, who unsuccessfully ran for governor in 2010, lost the House race in a year when Obama's approval ratings in Florida were negatively affected by consumer complaints about the health-care law's rollout. Sink also had criticized the Obama administration after her loss in the governor's race by about 1 percent.

With Jolly's win, Republicans keep control of a seat they've held for four decades in a beachside district dominated by retirees and Baby Boomers. Young died in October during his 22nd term. Jolly served as one of Young's aides before joining a lobbying firm.

Republicans will likely ratchet up attacks on vulnerable Democrats by honing in on the health-care law, MacManus said.

Former state Senator Mike Fasano, a Republican, said Jolly's ability to overcome attacks over his career as a lobbyist highlights the level of voter angst over Obamacare.

"Considering the fact that he's a Washington lobbyist, he has held in pretty strong, which tells me that a lot of it has to do with the Obamacare issue," Fasano said before the election was called.

'Washington lobbyist'

Sink and Democratic groups supporting her spent more than $5 million as they blanketed the district with television ads, mail pieces and radio spots painting Jolly as a Washington lobbyist with extreme views.

Taking place in the nation's largest presidential swing state, the race drew attention from a former president, a current vice president and several potential candidates for 2016's race. Bill Clinton recorded robo-calls backing Sink, and Vice President Joe Biden held a fundraiser on her behalf.

Florida Republican Senator Marco Rubio campaigned with Jolly and Republican Senator Rand Paul of Kentucky recorded a robo-call supporting him. Former Republican Florida Governor Jeb Bush endorsed Jolly in an ad sponsored by the U.S. Chamber of Commerce. Bush, Rubio and Paul are considering a run for president in 2016, as is Democrat Hillary Clinton, the former first lady and U.S. secretary of state.

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