By Barbara Liston
ORLANDO, Florida (Reuters) - In a race being watched as a potential bellwether for this year's mid-term congressional elections, Republicans cast their votes in a special primary election on Tuesday in a key Florida swing district.
The vote in the state's 13th Congressional District was to fill the vacancy left by the death in October of U.S. Representative Bill Young, a moderate Republican who had held the seat for 42 years.
Once reliably Republican, the district along Florida's Gulf coast has backed the party's presidential nominee only once since 1988. Former President George W. Bush, a Republican, won 51 percent of the district's votes in 2004 but it went for President Barack Obama in 2008 and 2012.
The Republican primary winner will face Democrat Alex Sink, the state's former chief financial officer and the 2010 nominee for governor, in a general election on March 11. Libertarian Lucas Overby also will be on the ballot.
Sink, considered the strong front-runner, has raised more than $1 million in campaign contributions, more than all three Republican candidates combined, according to the latest campaign filings.
"It's Sink's to lose," said Susan MacManus, a Tampa-based political scientist at the University of South Florida.
MacManus said the race is being watched to gauge the possible impact Obamacare may have in the November 4 midterm elections when all 435 U.S. House members - including the winner of this seat - will be on the ballot.
"People are looking at it as kind of a bellwether on whether Obamacare is going to hurt a Democrat in the general election," MacManus said.
Sink supports Obamacare and the three Republican candidates vying to become the nominee have said they would support repealing it.
MacManus said the 13th congressional district skews older, whiter and politically transitional, with registered Republicans currently outnumbering Democrats by only 37.1 percent to 34.7 percent.
Some Republicans have been disappointed that none of the party's heavy hitters chose to challenge Sink.
However, should Sink win, a new Republican candidate could emerge to take her on in November, MacManus said.
The Republican candidates on Tuesday's ballots are little known outside the district.
David Jolly, a Washington lobbyist, stresses his long experience as Young's congressional aide. State Rep. Kathleen Peters portrays herself as the candidate who best understands her district from her years in elective office.
Mark Bircher, an Iraq war veteran, presents himself as an outsider and the most conservative of the three Republicans.
Just 10 days before voters headed to the polls, any boost the Republicans hoped for from Young's popularity and family man image was lost.
The Tampa Bay Times reported in January about Young's personal life, including details about his first marriage. He quietly left his wife in 1985 to marry his secretary, who was half his age.
The divorce records were sealed, and the first wife remained quiet as a condition of alimony, the Times reported.
Young's potential posthumous impact on the race was further diluted when his second wife, Beverly, endorsed Jolly while one of his sons endorsed Peters in what the Times reported as a public rift between mother and son.
It was another fissure in the fractured local Republican Party as it prepares to face Democrats in the general election.
"There wasn't a consensus nominee here which will put the burden on the Republicans to put Humpty Dumpty back together," MacManus said.
Polls close at 7 p.m. EST.
(Editing by Gunna Dickson)