Suffolk University (pdf) (11/4-8, likely voters, 9/12-15 in parentheses):
Deval Patrick (D-inc): 38 (36)
Christy Mihos (R): 20 (17)
Tim Cahill (I): 26 (24)
Deval Patrick (D-inc): 36 (36)
Charlie Baker (R): 15 (14)
Tim Cahill (I): 26 (23)
(MoE: 4%)
This poor poll has been getting kicked down the road behind the scenes here at SSP for half a week now, but let's give it its due. It sees incumbent Democratic governor Deval Patrick in a weird position: his approvals are upside-down, at 42/51 -- worse than many governors currently seen as losing their 2010 races -- and he has an even-worse re-elect of 32/55. Nevertheless, he's somehow still thumping his opposition, winning three-way matchups by 10 points.
Patrick is one of the few endangered Dem governors who seems to be improving his position as the year wears on, and it seems to be all thanks to the presence of Tim Cahill, the Dem-turned-independent state Treasurer who seems to split the anti-Patrick vote, which, if added up, is the plurality of the vote. The state's few Republicans are sticking with the full-on Rs, while Cahill seems to pick up the Dems who can't stomach voting for Patrick or a Republican. This can be seen in the polls before Cahill got in, where Patrick trailed his Republican opponents, versus the ones after Cahill's entry -- the most recent of which, Suffolk's previous poll and Rasmussen, have Patrick up by double digits.
http://www.swingstateproject.com/diary/5914/magov-patrick-looks-better-thanks-to-cahill