I'd say popularity. At least that's the way it was when I was in school.
Do you think school elections is mostly based on popularity or how qualified the candidate really is?
Back in the old days, it was popularity....and I would venture a guess, that it's still that way.
I think that history repeats itself. Human voting is based mostly on emotion. And you must remember that only a small percentage of the population votes in the first place. And the vote of wealthier people matters more than the votes of poorer people. So just remember that in a modern democracy is doomed to repeat what the people "need". A democratic-republic is not destined to last forever. Just ask the Romans.
It was popularity when I was in school. Its sad