I believe Morgan Freeman has been cast as both?
It would have to be someone who was not obese for starters. Someone with a fine voice a fine mind a fine demeanor and a fine personality/character. IDEALLY.
So you could build one. Start with the voice. Then the appearance. Then the character. LIke the part Jimmy Stewart played in Mr. whatever goes to Washington. He had a strong decent morality and fought for what he thought was RIGHT not what would aggrandize himself. Unlike today's pols. Anyway moving on. Then the intellect. Then his/her likability. Then his/her CARING about ALL people.
You could create perfection which would be the model for reality. With luck. Maybe a movie about a DECENT president would bomb at the box office. The millions who adore dumb don would have no interest in it. But the others? Of course the dumb donners could BLOW UP every theater at which such a movie was being shown. There is that. They are volatile and weaponized and itching to answer his dog whistle. Sigh.