Italians have been voting in the final round of the contest for the leadership of the centre-left Democratic Party.
The run-off vote pitches veteran party leader Pier Luigi Bersani against Florence Mayor Matteo Renzi.
With the party leading opinion polls, the winner has a good chance of becoming Italy’s next PM in elections scheduled for early 2013, analysts say.
Those elections will choose a successor to PM Mario Monti’s government.
Mario Monti’s successor will face the challenge of addressing Italy’s deep-rooted economic problems.
Pier Luigi Bersani won the party’s primary on 25 November, winning 45% of the vote to Matteo Renzi’s 35.5%.
The two men are very different characters, with tieless, youthful Matteo Renzi, 37, painting himself as the voice of a new generation which wants to sweep away the entire class of older politicians.
By contrast, 61-year-old Pier Luigi Bersani is very much a figure from that older generation.
A minister in previous governments, he accepts that the leftist establishment that he represents has disappointed its followers in the past, but emphasizes the importance of experience.
Speculation has been mounting as to whether Silvio Berlusconi would run for a fourth term in office, with the ex-premier suggesting last week that he was thinking about returning to politics.
The billionaire tycoon’s record has been tarnished by sex and political scandals, and he resigned as prime minister in November 2012, after MPs approved an austerity deal to help curb the debt crisis threatening the eurozone.