When results start coming in, no doubt you'll be wanting to know how to read them so you're not jerked one way and then another, not knowing which party's strongholds have come in and what you can expect in coming hours.
I started to write a post explaining that a look at the 2002 gubernatorial race is instructive. In that race, a slick, glib, telegenic male Republican, Mitt Romney, defeated an uncharismatic female Democrat who had held statewide office, Shannon O'Brien. You can see the parallels. The margin was 50%-45%, with Romney taking eight counties to O'Brien's six.
(Please note that this is a map of the 2002 race for governor.)
Shannon O'Brien was from western Massachusetts, which may have run up her numbers there, but she won the western counties of Berkshire, Franklin, and Hampshire by double-digit margins, and Coakley should as well. The problem is, those are -- aside from the island counties -- the smallest in the state. (Curiously, the more rural areas of Massachusetts are among the most blue in the state.) Coakley should also follow O'Brien in racking up healthy margins in Suffolk County, otherwise known as Boston. O'Brien won by 60-35, so consider that the number to be exceeded.
In general in Massachusetts elections, the huge bellwether to consider is Middlesex County, which includes more than 50 cities and towns, including Lowell, Newton, and Waltham. Middlesex is important for two reasons. First, it has more than twice as many voters as any other county in the state. Second, it's a swing county. And third, Martha Coakley was Middlesex County District Attorney from 1999 to 2007. If she has a political base, you'd expect it to be there.
I said I started to write the post. This is how far I got, and then I read this amazing, invaluable post by Crisitunity at Swing State Project, which breaks things down to towns, the level at which voting will be reported. If you want to follow along with a guide to what percentage of the vote Martha Coakley will need in key towns if she's to have a chance at winning, it's unlikely you can do any better than this. It's an election-geek thing of beauty.