Maryland senator retires, drawing large slate of candidates for successor

Maryland Senator Ben Cardin will not seek reelection, creating a rare Senate vacancy.
Potential successors span the political spectrum, including progressives and moderates.
Personal wealth and election experience may factor heavily into a competitive race.
Speculation continues around possible entry of popular former Republican governor Larry Hogan.
Senate balance of power could hang in the balance of outcome in blue-leaning Maryland.