Bush because he has the finances and organization.
Walker because he has shown the best ability to govern.
Cruz because he is the best communicator.
I personally favor Cruz even though Walker is more qualified. However, I think the big money and the GOPe will prevail barring any major gaffes from Bush.
Ability to govern is something positive? Why do you think people like Walker and Perry are weak on immigration? They are governators. Anyone who has served a full term or more as a Governor is out for me.