The Wikipedia entry is very short, but he is in the line of succession of Delahunt and, most recently, Martha Coakley:
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William R. "Bill" Keating (born September 6, 1952) is an American politician from the state of Massachusetts. As of 2010 he is the District Attorney of Norfolk County, Massachusetts, having filled that office since 1999.
Following Martha Coakley's victory in the Democratic primary for the 2010 special Senate election, Keating announced that, should she win in January, that he would run for the vacant seat of Attorney General.
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He is, of course, a member of the Democrat machine, presumably made in the mold of Martha Coakley et al.
Here's his earlier state representative web page:
What are the odds that this Democrat flunky will actually "investigate" this scandalous affair. I'd say just about zero. First, a lengthy investigation. Then a quiet announcement that nothing suspicious has been found. Especially nothing suspicious against Delahunt.
This thing has gone national. They can’t broom it this time. The FBI has to be nosing around now.
He may talk like he's doing just that, but he'll cover up anything he possibly can.
Thanks...I’d say that’s right about Keating probably coming up with nothing but his investigation may not end it, it’ll be interesting to see how this progresses.