The PA is controlled by the Israeli government and follows orders. On top of that their personal interest pushes them to destroy (or try to) Hamas. If elections supervised by international observers were held, the PA would disappear and Hamas would win by a landslide in Gaza and WB. That's why there are no elections. the PA leadership has been in power for almost two years after their mandate expired.
4 UN peacekeepers injured in Sinai and taken to hospital in south Israel (Haaretz)
from the article: The Palestinian Authority is imprisoning Gazans