Italian Premier Romano Prodi resigned after his center-left coalition lost a Senate confidence vote, a humiliating end to a 20-month-old government plagued by infighting. Italy now faces the prospect of early elections or the formation of an interim government, a decision that must be made by President Giorgio Napolitano. Prodi will stay on in the meantime in a caretaker role. Elected in April 2006, Prodi had a shaky government from nearly the start. It lurched toward collapse this week after a small Christian Democrat party, whose votes were vital to his Senate majority, yanked its support in the latest coalition spat. The government lost 161-156 Thursday after a fiery debate during which one senator was spat upon, fainted and had to be carried out on a stretcher. Lawmakers from the conservative coalition of former Premier Berlusconi cheered and popped the cork on a bottle of sparkling wine as the defeat was announced.