Who is Robert Browne from The Widening Gyre and what is their importance?

Robert Browne is a Massachusetts congressman. He serves his state almost as much as he serves Joe Broz, the organized crime boss who makes substantial campaign contributions. Browne and Spenser only meet once, at which time he tells Spenser to stop his investigation of Joe Broz's son. Unfortunately, he gives away more information during their exchange than he intended.