CLEARWATER

Republican David Jolly won the nationally watched, stunningly expensive and relentlessly negative battle for Pinellas County's open congressional seat Tuesday, signaling possible trouble for Democrats across the nation in the fall elections.

The loss could be a career-ender for Democrat Alex Sink, 65, who ran a well-organized and hard-fought campaign, but lost her second close race in a row.

It means Jolly, once an obscure aide to the late Republican U.S. Rep. C.W. Bill Young and then a Washington lobbyist, will fill the seat occupied for more than four decades by his former boss.

"I have very good news tonight. No more commercials," Jolly said at his victory party, where he was introduced by former game show host Bob Barker. "Congressman David Jolly, come on down," Barker said via video.

"This has been a remarkable journey, not just for me, for our entire Pinellas County community," Jolly said before a crowd at Clearwater's Sheraton Sand Key Resort. "I am honored and am humbled to have received the support."

Final unofficial results showed Jolly with more than 48 percent of the vote to Sink's 47 percent, or roughly 3,400 votes separating them.

In contrast to the divisive campaign, Jolly spoke Tuesday night of unifying Pinellas and working together.

"For all of the national interests in this race, this is a Pinellas County community. . . . What brings this county together like so many other communities is we are sick and tired of the vitriol and rhetoric on both sides."

He said he would "lead by example on that" and said he hoped voters "saw a heart of service tonight that perhaps they once saw in Bill Young."

Sink conceded shortly before 8 p.m., calling it "disappointing" but heaping praise on the more than 2,000 people who volunteered for her campaign and knocked on 150,000 doors.

"But for all that, it just wasn't quite enough to take us over the victory line," Sink said to a crowd of about 200 at the St. Petersburg Hilton Carillon.

Aides whisked Sink away before reporters could ask whether she would run again in November.

"I'm stunned," said Mary Freeman, a member of the Pinellas Democratic Executive Committee. "I have never seen a candidate work so hard, really. It was 24/7. She visited so many businesses and communities in the district, and even had Republicans saying they were going to vote for her."

The contest drew national attention and eye-popping spending — more than $12 million, the bulk from outside groups that drowned out local issues and underscored a fundamental shift in control away from candidates.

U.S. Rep. Greg Walden, R-Ore., chairman of the National Republican Congressional Committee, said 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."

Sink and her allies attacked Jolly for his lobbying career and contended he wanted to undermine Social Security and Medicare, essential programs to the district's older voters.

But Jolly and outside Republicans hammered away at Sink's support of the Affordable Care Act and had an unpopular president in their corner as well.

Jolly, 41, will have to face the gantlet once more when the seat is up again in November. The 13th Congressional District, which stretches from south Pinellas to Dunedin with portions of downtown and southern St. Petersburg cut out, is pretty evenly split between Democrats and Republicans.

Sink had the initial lead Tuesday when votes came in from mail-in ballots and early voting. The lead almost instantly evaporated as results came in from Election Day, when Republicans traditionally fare better.

More than 125,000 voters turned in ballots before the polls opened Tuesday. Of those, more than 53,000 were Republicans and more than 48,000 were Democrats.

Both sides mounted last-minute get-out-the-vote efforts, including having volunteers from across the country make calls to Pinellas voters.

The race drew widespread national media attention, framed as a test run for November's midterm elections, each side testing messages and tactics. Former Gov. Jeb Bush and Sens. Marco Rubio and Rand Paul got involved for Jolly. Former President Bill Clinton recorded a robo call for Sink, and Vice President Joe Biden raised money for her.

The race is considered the most expensive special House election on record, with $9 million of the more than $12 million spent coming not from the candidates but from outside groups that unleashed a torrent of negative ads.

The attacks were misleading and unrelenting to the point that the candidates complained local concerns were being overshadowed and their own positive messages buried. Jolly in particular said he could not present himself the way he desired. Without the outside players, however, he would have struggled to remain competitive due to Sink's superior fundraising.

A polished speaker, Jolly carved out a conservative stance on many issues, saying he wanted to repeal Obamacare, he opposed abortion rights in most cases and saw no federal role in addressing climate change.

The one candidate who didn't get caught up in multimillion fundraising was libertarian Lucas Overby, who mounted a well-organized third-party effort, seeking to draw support from people who were fed up with the very tactics employed by his opponents. But his efforts netted him less than 5 percent of the vote.

Times staff writers Julie Kliegman, Claire Wiseman and Mark Puente contributed to this report.