By Scott Malone
BOSTON (Reuters) - The three Republican contenders for the Massachusetts Senate seat that opened up when John Kerry was named Secretary of State were set to face off in their first debate on Tuesday.
The trio - Boston's former top federal prosecutor, a state representative and a private equity executive - face an uphill battle in liberal-leaning Massachusetts, where polls show Democrats with a strong lead ahead of the June 25 special election for the vacant Senate seat.
Among the Republicans, former Attorney Michael Sullivan had the strongest support among likely voters in a University of Massachusetts Lowell-Boston Herald survey conducted last week, followed by private equity executive and former Navy SEAL Gabriel Gomez, with State Representative Daniel Winslow in third.
But all three Republicans trailed Representative Edward Markey, a Democrat, who also holds a lead over fellow Democratic Congressman Stephen Lynch.
Pollsters caution that all five candidates had relatively low name recognition among likely voters, meaning that the lead could easily change.
The Republicans were set to kick off an hour-long debate on Tuesday at 7 p.m. local time (2300 GMT) at Stonehill College in Easton, Massachusetts, about 30 miles south of Boston.
They will ask each other questions and face questions from moderator Peter Ubertaccio, a professor at Stonehill.
"We are going to deal with economic issues, social issues, have some conversation about the Republican party and its direction," Ubertaccio said.
Sullivan, who holds more conservative positions on social issues than Gomez and Winslow, is the one candidate in the race to oppose gay marriage, which is legal in Massachusetts.
The Republicans' views are more in line on economic issues, with all three arguing for spending cuts to lower the federal government's $16 trillion in debt.
In the state's last special Senate election three years ago, Republican Scott Brown stunned the liberal establishment by winning the seat that liberal lion Edward M. Kennedy held for almost a half-century.
This time, a Republican victory could help the party's effort to retake a majority in the Senate, where it holds 45 seats. Democrats have 43 seats, and there are two independents.
In January, Massachusetts Governor Deval Patrick named his former chief of staff, William Cowan, as interim senator. Cowan is not running for the seat on a permanent basis.
(Reporting by Scott Malone; Editing by Ellen Wulfhorst and Jan Paschal)