PaulusIII
Unholy Warlord
1. Hannibal founded Confucianism in that round (via DR) and converted. This has broken up the Jewish block, which is unfortunately somewhat of a mixed bag. The religious tension will likely lead to warfare at some point. This could weaken both of them, but if one wins the war (especially Hannibal) it could create an unstoppable force. And it will probably complicate the diplomatic situation at some point.
I doubt there's much military difference between Mehmed and Hannibal so a war would only do good to keep Hannibal (and to a lesser extent also Mehmed) from running away in tech, especially if it grinds down into a stalemate just like the war between Justinian and Ragnar.
2. The AP hasn't been built yet.An Islamic AP would complicate matters greatly, and could require a major change in strategic planning.
He can still defy every single vote.

What might be the biggest problem in the long term is - yet again! - tech trades and WFYABTA. Saladin, Darius and Mehmed are already in WFYABTA (and I suppose Ragnar as well, but he's useless for techs) which leaves only Justinian, Hannibal and Pacal as tech trade partners - because without religious bonuses, getting someone friendly is hard. Of these, Justinian is falling behind (and as long as he's still grinding it out with Ragnar I doubt he'll ever catch up), Pacal has a low WFYABTA limit as well so you'll bump into his limit as well, and Hannibal is far ahead. I hope the tech trades aren't going to dry up anytime soon.