I just ran into an issue with Zolot. I did his personal quest early to secure his vote, he withdrew his vote from me to pledge it to onol Gfvexbal, and after I let Rfznenev trg nffnffvangrq ng gur bcren, I went back to see if I could reclaim it. If I try to negotiate, I get the message that he's not taking my calls until I've finished his personal quest:
However, there's no option for the personal quest since I've already completed it and turned it in. He did accept a flattery call and a call with an offer of a cabinet position.