FIVE years after Mahmoud Abbas, the Palestinian president, dismissed an elected government run by the Islamists of Hamas and decided to rule instead by decree, the Palestinian Authority (PA) that oversees the West Bank is being dangerously challenged from within. In Nablus, the first city where Mr Abbas chose to fill the security vacuum with his American-trained national-security battalions, turf wars have recently erupted between rival commanders, puncturing four years of calm. The walls of Jacob’s Well, a local church, a theatre and the UN office all bear the scars of recent shooting sprees. “It’s hell,” says a social worker in Balata, the city’s largest refugee camp, which suffered grievously during two previous intifadas (uprisings), in 1987-93 and 2000-05. Now people are beginning gloomily to wonder whether there will be a third intifada, this time aimed at the PA as much as at the Israelis occupying the West Bank.