Polls in titanium states mostly tend to underestimate the winner (California is a prime example). Biden will easily crack 60% in Massachusetts. I wouldn't be surprised if he got 63-65%.
And for the same reason, polls usually underestimate Republicans in places like Alabama and Oklahoma. I suspect the reason for this is that the undecided group in any state has some resemblance to the state's overall voter population. So in MA or CA, the majority of those who are undecided now are going to have attitudes that make them likely to vote D in the end; similarly, the undecideds in AL or OK will tend to naturally favor R. In the end, more votes from this group go to the dominant party in the state, and it overperforms the polls.
