The center-left, shattered by Prodi's resignation after less than two years in office, favors an interim government to enact reforms and delay the vote.
Walter Veltroni, the likely center-left candidate for premier, has long demanded a reform of the electoral law. He insists that electoral reform can be passed in a few months in the interest of the whole country.
The current proportional-representation system was passed during the waning days of Berlusconi's government but was criticized then even by some of its proponents. It is seen as giving disproportionate weight to small parties, thus fostering instability.
While most agree it must be changed -- Veltroni and Berlusconi even held talks months ago to discuss possible changes -- no alternative system has won enough consensus.
Prodi, whose government was long hampered by coalition infighting, resigned Thursday after he lost a confidence vote in the Senate due to defections by some allies.
Napolitano has since been meeting with political leaders to find a way out of the crisis. He said Wednesday that he could not call elections without trying to change the much-criticized election law.
