In the new poll, conducted by Garin Hart Yang Research Group for the League of Conservation Voters and NARAL Pro-Choice America, both of which have endorsed Markey, Markey takes 42 percent support to Lynch's 28 percent support among likely Democratic primary voters.

That's nearly identical to the last LCV-sponsored poll, conducted in mid-February by Democratic firm Public Policy Polling, which gave Markey 43 percent support to Lynch's 28 percent support.

The new poll, conducted in late February, indicates that Markey is better-known and better-liked than Lynch, but Lynch has an opportunity to gain some ground on the frontrunner if he's able to define himself before Markey can in the primary contest.

The survey was conducted among 613 likely Democratic primary voters in Massachusetts from Feb. 26-27, and has a margin of error of plus or minus four percentage points.