An anti-establishment movement is the favorite as voters head to the polls to pick a new mayor in Rome, among a handful of city hall contests in Italy that will test the prime minister's governing Democratic Party.

A broad corruption scandal and deteriorating public services have soured many voters on traditional parties in Rome, driving support to the grassroots, populist 5-Star movement.

Local elections will also be held Sunday in Milan, Naples, Bologna and elsewhere.

Run-offs are expected on June 19 in most contests, unless candidates manage to win more than 50-percent of the vote.

While Premier Matteo Renzi could emerge weaker from the races, analysts say the real test will be a referendum on constitutional changes launched by his government and heading to a vote in the fall.