They buying of mob help in several states was done with $250,000 bags of cash in small bills direct from JFK with girlfriend Judith Campbill being used as a courier. Discussions of it were picked up on FBI iretap tapes and mention of the tales was made in, I believe, a fall 1998 Time Magazine piece quoting a retired federal agen with knowledge of the matter.
One story. RFK tried to get Carlos Marcello (New Orleans mafia boss) deported. The federal court said no deal. Kennedy had some INS pick him up and take him to, I think, Guatamala and left him alone penneyless in the hills. He found his way down to the coast and a phone and his guys came and got him. Since CM reported to Giancano in Chicago, RFK was directly screwing with the underboss of the guy who got his brother elected.
This is often cited as CM's motive to have JFK killed.