As of 9:00am, 23,667 people had voted in Boston. That's about 30% ahead of the 18,399 who had voted by 9:00 for November's Mayoral election.
That would project to be about 140,000 voters, or roughly 40% turnout in Boston.
Secretary of State Bill Galvin is predicting roughly 40% turnout statewide.
Boston often votes at a lower rate than the state as a whole. In the 2008 Presidential election, for example, turnout in Boston was 62%, while statewide it was around 73%.
Martha Coakley needs Boston (and cities like it) to turnout well relative to non-urban parts of the state -- particularly in southeastern Mass., where Brown is expected to do well.
What I don't know (yet) is whether other parts of the state are turning out in line with Galvin's 40% projection, or significantly higher? Anecdotally, I'm hearing about strong turnout, but I've got nothing solid.
Also, of course, there's the question of how solidly Coakley will carry places like Boston. The last time Ted Kennedy was on the ballot, he won 84% of the Boston vote -- but that was against obscure Republican Ken Chase. Brown will do much better; how much better remains to be seen.