PD leader Matteo Renzi, who has been seeking to make a comeback since stepping down as prime minister in December, was the clear loser in Sunday's vote, though polls show his party is still one of Italy's most popular nationally.
"It could have gone better," Renzi said in an early-morning Facebook post. "The overall result isn't great. Some losses hurt, starting with Genoa and L'Aquila," he said, referring to another former left-wing bastion city that fell to the right on Sunday.
The Northern League's leader, Matteo Salvini, said the Genoa result was proof that Prime Minister Paolo Gentiloni had lost the country's support and should step down.
"Today Gentiloni should resign," Salvini said. "Italians want change." The center-left has governed Italy for four years, during which time the economy grew by only half the euro zone average. Three different PD premiers have struggled to shore up a banking system strangled by bad loans, and to manage half a million migrants who came by boat from North Africa.
Beach or ballot
At 46 percent, turnout was very low by Italian standards, with many of the 4.3 million eligible voters probably choosing to go to the beach on the sweltering summer Sunday rather than the ballot box.
Sunday's vote was one of the last before a general election due by the end of May 2018, but it may not be a reliable indicator of what will happen then.
The first-past-the-post voting system used at the municipal level, which favors coalitions, may not be replicated at a national level, where a proportional system is now in place.