Such a primary matchup would be heavily favorable for Markey, however, who has 52 percent support to Lynch's 19 percent among Democratic voters polled. And while 58 percent of Democrats view Markey positively, only 27 percent view Lynch positively, with slightly more viewing him negatively.

And Lynch fares worse than Markey against Brown, lagging the Republican by 9 percentage points in a potential matchup.

Brown has not yet indicated his future political plans, and while he remains the most likely Republican contender, the PPP poll indicates a plurality of Republicans, 48 percent, would prefer he run for governor. Thirty-eight percent would prefer he run for the senate.

The poll was conducted among 763 Massachusetts voters from Jan. 29-30, and has a margin of error of plus or minus 3.6 percentage points overall, and plus or minus 4.9 percentage points for just Democratic respondents.