JERUSALEM – Influential members of the militant Islamic group Hamas on Sunday balked at the nominee of the rival Fatah party for prime minister in a shared government, the first significant snag in carrying out a reconciliation pact signed last month by the Palestinian factions. Fatah on Saturday nominated the current prime minister, Salam Fayyad, a political independent, as its candidate to head the new government, a move designed to maintain Western aid to the Palestinian Authority.