As squabbles go among the weak and fractious parties that make up Egypt’s enfeebled political opposition, there was a particularly dramatic incident last month. Armed with Molotov cocktails, steel bars and aerosol cans used as mini-flamethrowers, dozens of men attacked the al Ghad party’s headquarters in Cairo, sending plumes of smoke billowing from the building’s windows.

Rival factions blamed each other for the attack, which took place in broad daylight. One group is loyal to the party’s founder, Ayman Nour, the jailed candidate who challenged President Hosni Mubarak in 2005 elections. The other is loyal to the government, and the two have bitterly contested which group is legitimate.