Tell your son that what he should seek is not power, but authority. The difference is that power is taken, authority is given.
He can do more by being a priest than by being President. What needs to be changed in the world are souls, and the only effective way to do that is one at a time. Although the number of priests worldwide has experienced an increase of late, the number of priests in the Americas and Europe is on a slight decline. Our souls are immortal, and to help a soul to heaven will last forever. To affect the government of a secular society will be a very short-lived thing, IF he could even do it.