Polls on polls on polls. Jerold Duquette, an associate professor of political science at Central Connecticut State, writes for the MassPoliticsProfs blog: 

The implication here is that a lack of enthusiasm for the Democratic president could depress Democratic turnout, which could redound to the benefit of Republican Charlie Baker. There’s nothing wrong with this logic; it’s essentially a no-brainer in fact, but the suggestion that Coakley is being “dragged down” or that her chances of victory are being “hobbled” by national trends is almost certainly overblown.

Read more on the MassPoliticsProfs blog here