Of the nominees, I did not get a chance to see Ken Watanabe. I had initially thought Robert Fairchild would have the lock, but so many have been inventing superlatives to describe Fun Home and its cast, Tony voters often love "heavy" over "light" and Michael Cerveris is fairly well-respected in the theater community that it all may combine to give him the edge that I am not sure is entirely deserved in this case.
Personally, I would root for Fairchild (who I think is a fantastic addition to Broadway and nailed the part), followed by Tony Yazbeck (his Lonely Town was divine, plus he is designated water bearer for a show whose cast is absurdly under-represented in the performance nominees) and Brian D'Arcy James. Again, I have not seen Ken Watanabe and truthfully (let the brickbats and raspberries fly) I have often found Michael Cerveris to be solid, but overpraised and overrated in what I have seen, and Fun Home was no exception.