There is already a design in the works related to this but it's early to talk about it(and not my place to talk about it since I'm not the one in charge of those changes). Our design team recognize this aspect of the decision making mechanic and working on a new design.
They understand that players feel powerless in situations where even though they have the influence/power to change decision outcomes, they have no way of doing it while the decision making is taking place. This can include swaying voters that are supporting other outcomes, or even lords who are "undecided". And since the player can do this, AI lords can also sway other lords too, depending on their influence in the kingdom.
This is my take on it and might change in the future but know that we're planning on changing some aspects of the decision making in kingdoms.