So I've been slowly acquiring bits of Lombardy as the Byzantine Emperor. Lombardy has elective succession. I am now an elector in Lombardy, and 4 of the other electors are also my vassals and of same culture and religion. However, while I can vote for myself, they still refuse to vote for me, preferring to vote for themselves (they won't for the King of Lombardy's choice either). They don't have the ambitious trait, so I'm puzzled. What do I have to do to get them to vote for me so that I can acquire the Kingdom of Lombardy?