Republican David Jolly and Democrat Alex Sink chat during a break as they participate in a candidate forum on Feb. 25. (Brian Blanco/Reuters)

— The Tampa Bay peninsula will serve as the first real test of 2014 voter moods on Tuesday in a down-to-the-wire congressional race that each side is using to hone its messages for November.

Republicans, returning to their 2010 and 2012 model, are trying to turn Democrat Alex Sink into a clone of President Obama and House Minority Leader Nancy Pelosi (D-Calif.), focusing heavily on Obama’s health-care law. Democrats, for the first time since the law’s bungled rollout last fall, are fighting back with a defense of the law that accuses Republican David Jolly of wanting to repeal the Affordable Care Act and “take us back” to the era when preexisting conditions could lead to a denial of health insurance.

Polls show Sink and Jolly in a tight race to claim a district that is the most evenly divided in any special election held since 2012. Obama narrowly won the district in 2012, and Sink carried the district in 2010 in her losing bid for governor. But for more than four decades the House seat had been comfortably held by C.W. Bill Young, a genteel Republican who specialized in delivering earmarked federal funding for his constituents.

Young, who never faced a real challenge, had announced his intention to retire at the end of this year. Then, in October, he died, setting off a scramble for a special election that concludes Tuesday.

The implications of the race are considerable, even by the standards of overanalyzed special elections.

Republicans say that if their first-time candidate defeats a seasoned veteran, it will demonstrate just how toxic the health-care law will be for Democrats this fall.

The race is particularly important for Pelosi’s Democrats, who have battled the perception that they have no chance of winning the close to 20 seats they need to claim the majority in November. This district, while leaning Republican in midterm elections, is exactly the sort that Democrats need to win to punch through to majority status, now that it is no longer safely in Young’s possession.

That’s why they recruited Sink from neighboring Hillsborough County to move across the bay, bringing with her a strong fundraising base and the potential for crossover appeal to independent and female Republican voters. That’s why Sink spent hours in this Gulf Coast beach town last week, tossing beads to hundreds lining a Mardi Gras parade and doing more face-to-face politicking than she ever did in the governor’s race four years ago.

“Nobody ever got to see that I was approachable,” Sink said, dashing across Dunedin’s Main Street on Thursday, avoiding rain puddles in a yellow slicker.

A victory by Sink would give Democrats a chance to argue that they know how to deflect the attacks about the Affordable Care Act and pivot to an offensive message focused on running as post-partisan problem solvers. Standing in a candy store, Sink rifled through criticism of the health law — she wants more flexibility for small businesses to keep hiring without tripping into requirements to buy health insurance for workers — but she defended the law’s overall thrust.

“We can’t go back to where we were before,” she said, citing past double-digit inflation in health costs. “Let’s take the parts of the Affordable Care Act that may not be working correctly and fix them.”

This fix-it-don’t-repeal-it message has emerged as the clarion call for Democrats, who say it is the right mix of acknowledging faults in the law while defending the overall effort. Sink’s campaign is the beta test to see whether voters in a swing district will support that assertion, and she has had plenty of funding to test the message.

Voters have been subjected to more than $9 million in ads flooding the airwaves.

Sink has raised at least $2.7 million in less than four months. She also did not face a tough primary and has leveraged that into an advantage over Jolly, who had to endure a bruising contest on his way to the nomination.

She has spent $2 million on television ads, four times as much as Jolly, a former staffer to Young with a long history as a Washington lobbyist. Official GOP committees and outside conservative groups have come to Jolly’s aid, but overall Democratic TV spending has outpaced GOP spending by roughly $800,000.

At an event Wednesday with volunteers, Jolly bemoaned the financial disparity. “There’s a lot of noise out there, and the unfortunate thing is I’m not sure the voters know exactly where we stand on the issues,” he told reporters inside his Clearwater headquarters. “Listen — the ability of opponents to paint each other, you know, with misrepresentations has been very effective.”

Voters have noticed. As Sink tossed beads at the Mardi Gras parade — remaining atop her campaign’s white Thunderbird, never working the crowd — several Republicans bemoaned their choices. “I can’t stand Jolly. I can’t stand Sink,” said Lisa Tighe, 52, a management consultant who voted for GOP presidential nominee Mitt Romney in 2012. A supporter of abortion rights, she plans to vote for the Libertarian nominee, Lucas Overby, who polls show could get as much as 5 percent of the vote.

Another Romney voter, Frank Stewart, 48, an operations manager at a printing company, plans to sit out the special election. What does he know about Jolly? “Only what I hear from the ads,” he said.

In another sign of things to come this fall, Obama has remained out of sight in this part of Florida, even though he spent the weekend vacationing not too far away in Key Largo.

Despite the national focus of the ad campaigns, most voters have closely watched the congressional debate over retooling the national flood insurance program, which is set to have skyrocketing premiums for coastal communities. Aware of the impact on this race and other congressional contests, House GOP leaders used Democratic votes to pass a bill Tuesday that sets lower increases — leading the local newspapers and TV newscasts.

One reason this race is such a bellwether for November is that both candidates are seen as having critical flaws and lack charisma on the stump, minimizing the personality difference and making it more of a referendum on their messages and the issues aired in the campaign.

To some degree, the race is outsider vs. outsider. Sink is not from Pinellas County, a fact that Jolly supporters drive home endlessly, and some Democrats blamed a bland personality for her 2010 loss to Rick Scott in the governor’s race. Yet Jolly’s lobbying practice in Washington has been just as ripe for Democratic operatives to plumb for 30-second ads.

In a bid to offset these disadvantages, Jolly has wrapped himself in the glow of his former boss, distributing literature that hails him as a “Bill Young Republican.”

The late congressman’s personal life has served as a bizarre backdrop during the campaign, as his family splintered publicly over backing a successor and stories emerged about a bitter feud between Young’s widow and his first wife. One son, Billy Young, who is running for the state legislature, backed Jolly’s rival in the GOP primary, while his widow, Beverly, and others supported Jolly.

Despite the family soap opera, each candidate is claiming to be the rightful heir to Bill Young’s nonpartisan approach. On Wednesday, son Pat Young, 26, was volunteering for Jolly in Clearwater. “At the end of the day, it’s not about being a Democrat or Republican,” he said.

In Dunedin’s Candy Bar store, Sink made sure to eat some Angel Mints, made by the local candy manufacturer that was so grateful for Young’s support over the years that it created a brand named for the lawmaker.

“It’s going to be tough,” Sink said. “It’s going to be a very close election.”