Great idea. I don't know where the story is on the internet but the late Master Nan says in one of his lectures that some Buddha and his disciples, samadhi powers and all, tried to change India.
They failed. People are just too lazy and their karma way too thick to cut through mere skillful means. You help a person, and you enable their laziness and create a karmic debt for them! You jerk. You ignore them and let them suffer, they become motivated and help a million people.
Every action has an opposite reaction.
Other people can't save you without un-saving you later.
Buddha just can't save you, otherwise he'd have done it. There's something big going on!!
Buddha just can't kill your bad karma or anyone's bad karma.
He can only act as a intermediary and help purify that karma because of positive states of mind: shame, renunciation, faith, wisdom, concentration, meditation on the Buddha's positive qualities, etc. Buddha actually does little but act as a meditation object. The true power of mantras, according to Master Nan, can't even be accessed except by those in a deep state of dhyana/jhana/samadhi.
This is the same for confessions in Catholicism. Mother Mary can't do anything!
It was just a skillful means as mentioned in the previous paragraph.
If the Buddhas could effectively help people through political leadership--it would have already happened. It's because of some sort of karmic binding where people are self-responsible and must change their own fate, that they have not/cannot do it.
Politics is dirty, people are greedy, corrupt, and self-rationalizing! Even if Buddhism could become a political party--I doubt it stay for long. It would eventually become hijacked, derail, or decay.
The Three Poisons are stacking, moment by moment, millions of times in a day unawares until they cause people to behave in surprisingly evil ways. Countries have their own karma and everyone is contributing to it, it is hard for a small amount of people to purify the whole country's bad karma, especially when they are working against so many suave, manipulative, and cold-blooded murdering politicians.
The only salvation is self-awareness whilst not attaching to anything, not taking anything for self. Who cares about others anyway? Everyone will save themselves, give it a few million eons. All the while you enjoy yourself as a Buddha in Perfect Enlightenment, manifesting a million nirmanakaya bodies helping-beings-throughout-the-universe-through-causes-and-conditions.