Candidate 5 is Jesse Jackson Jr., according to this report.

According to the [Blagojevich] criminal complaint, on Oct. 31st, Blagojevich was overheard saying of Candidate 5, “We were approached ‘pay to play,’ that, you know, he’d raise me 500 grand. An emissary came. Then the other guy would raise a million, if I made him a senator.”