Rep. Edward J. Markey led by double digits in a new poll in the Democratic primary for the Massachusetts Senate special election.

According to the WBUR poll, 35 percent of likely Democratic primary voters said they would support Markey, 24 percent backed Rep. Stephen F. Lynch and 41 percent remained undecided.

The results follow a poll from earlier this month showing Markey ahead of Lynch by a nearly 30-point margin.

The winner of the April 30 Democratic primary will be heavily favored to win the seat of former Sen. John Kerry, D-Mass., who is now secretary of State. In this poll, both Markey and Lynch led their potential GOP opponents for the June 25 special election by wide margins.

Former U.S. Attorney Michael Sullivan led with 28 percent among likely GOP primary voters, followed by state Rep. Dan Winslow with 10 percent and Gabriel Gomez, a private equity investor and former Navy SEAL, with 8 percent. Forty-six percent were undecided.

The poll of 610 likely voters was conducted March 19-21. The full sample had a 4.1-point margin of error, but the margins of error for the primaries were not provided.