While Republicans held the congressional seat for more than four decades until the death of Rep. Bill Young last year, the Clearwater Beach district's voters favored Obama in the 2008 and 2012 presidential elections. Democrats were hopeful, clearing the field for Sink, the state's well-known chief financial officer and the party's gubernatorial nominee in 2010. Republicans failed to recruit their top picks, leaving Jolly to fight a bruising three-way primary.
This stretch of beach towns and retirement communities on the Gulf Coast is the type of terrain where Democrats need to compete if they hope to win seats in the House and keep control of the Senate. Analysts said the loss could bode badly for the party, which is already saddled with an unpopular president and a slow economic recovery.
"The overall picture does send a message and it says, 'Be afraid. Be very afraid,'" said Jack Pitney, a former national GOP official and government professor at Claremont McKenna College in California. "This is one more piece of evidence that 2014 will be a very difficult year for Democrats."
Democrats, however, downplayed the loss, saying the GOP fell short of its traditional margin in a Republican-leaning district packed with older voters. With almost 100 percent of the vote counted, Jolly had 48.5 percent of the vote to Sink's 46.7 percent. Even before the defeat, party officials had been lowering expectations.
"I've never believed that special elections are a bellwether of anything," said Rep. Steve Israel of New York, who chairs the House Democrats' campaign operation. "You have to treat every district for what it is, not for what you want it to be."
Nevertheless, the battle for Florida's 13th District seat in the Tampa area was a prequel of sorts to the national fight this year over who controls Congress in the last two years of Obama's final presidential term. The House is expected to remain under Republican control. But in the Senate, Republicans are hoping to leverage Obama's unpopularity and his healthcare law's wobbly start to gain the six seats required to control the 100-member chamber.
That made the race in Florida a pricey proving ground for both parties heading into November elections.
Jolly, a former Young aide backed by Republicans and outside groups, campaigned on a conservative platform, promising spending cuts, balanced budgets and repealing the healthcare law.
The message against the healthcare overhaul proved a rallying cry for Republican voters, who surged to the polls on Election Day.
"No more big government. We've got to stop," said Irene Wilcox, a 78-year-old retired waitress and Republican from Largo who voted for Jolly.
Others described Sink as a clone of Obama and House Democratic Leader Nancy Pelosi, a key argument of Jolly and national Republicans.
"As bad as Bush may have been, he was a saint compared to the guy we have in Washington," said Rich Castellani, a retired treasury agent and independent voter who supported Jolly.
Meanwhile, Sink pitched herself as a bipartisan problem-solver, trying to appeal to Republicans and independents. She painted Jolly as an extremist who wants to "take us back" to when people were denied health coverage due to existing conditions. She pledged to "to keep what's right and fix what's wrong" in the healthcare law.
That argument resonated with some voters.
"While I know it's not perfect, it's maybe the beginning of where we can provide adequate healthcare to everyone, not just the wealthy," said Frieda Widera, a 51-year-old Democrat from Largo who backed Sink.
In an attempt to deflect criticism over the law, Sink and Democrats painted Jolly as a Washington lobbyist who backs efforts to privatize Social Security and gut Medicare. The attack put Jolly on the defensive in recent weeks, and some voters cited concern about GOP cuts to programs for the elderly. More than one in four registered voters in the district is older than 65.
"The Republican Party thinks they are hurting President Obama," said George Nassif, an 82-year-old Republican who voted for Sink. "They are not. They are hurting the people."
In his victory speech, Jolly didn't mention the president's healthcare package, instead focusing on a need for people in Pinellas County to work together.
"This race is not about defending a broken agenda in Washington or advancing a broken agenda in Washington. This race is about serving the people in our own community," he said. "Let's dispense with the rancor and vitriol of the last five months."
In St. Petersburg, Sink's party was subdued. Backed by her adult children, she delivered her concession speech to a couple hundred stoic supporters in a half-empty ballroom at a lakeside Hilton.
Many voters expressed disgust at the amount of money spent on the race — and the relentless barrage of television ads and mailers that were on par with a presidential election.
Sink outspent Jolly by more than 3 to 1 on television advertising, though outside groups aligned with the GOP helped narrow the overall Democratic advantage.