BOSTON, March 26 (Reuters) - Democratic Representative Ed Markey retained the lead among the five candidates seeking the Massachusetts U.S. Senate seat previously held by John Kerry, although a large number of likely voters remain undecided, according to a poll released on Tuesday.
Ahead of the April 30 primary, Markey held an 11 point lead over rival and fellow Congressman Stephen Lynch, who had gained some ground after trailing a wider margin in earlier polls, the WBUR/MassInc Polling Group found.
Among likely Republican voters, former U.S. Attorney Michael Sullivan held the support of about three times as many voters as rivals state Representative Dan Winslow and private equity executive Gabriel Gomez.
But large numbers of voters from both parties remain undecided ahead of the primary, with 41 percent of Democrats and 46 percent of Republicans saying they did not yet know who they would vote for.
Both Democratic candidates topped their possible likely Republican rivals in questions about head-to-head match-ups in the June 25 special election, the poll of 610 likely voters surveyed from March 19-21 found.
The poll has a 4.1 percent margin of error.
All five candidates will face off in their first debate on Wednesday night. (Reporting by Scott Malone; Editing by Maureen Bavdek)