By James Mackenzie
ROME (Reuters) - Beppe Grillo's 5-Star Movement won control of one of the historic strongholds of the Italian left in local elections at the weekend, although Prime Minister Matteo Renzi's center-left Democratic Party (PD) stayed Italy's strongest political force.
The 5-Star Movement's candidate Filippo Nogarin became mayor of Livorno, the Tuscan city where the Italian Communist Party was founded in 1921 and which the left had held virtually unchallenged since World War Two. The party also won Civitavecchia near Rome.
Despite the loss in Livorno and other defeats in towns like Perugia and Padua, Renzi's party won in the cities of Bari, Modena, Pavia and Bergamo, to take well over half of the 139 towns and cities voting in the run-off ballot on Sunday including 10 of the largest centers.
Centrist, center-right or rightwing parties won most of the remainder, including six larger towns.
"The center-left has confirmed its position in big cities like Bari and Modena," Stefano Bonaccini, the PD spokesman for local elections, said in a statement. "There's disappointment for defeats in Perugia, Padua and Livorno but they don't take anything from the strength of the PD and the center-left across the whole country," he said.
Italian media said a bribery scandal in Venice, in which the center-left mayor of the city has been placed under house arrest, had dented results for the PD after its triumph in the European parliamentary election in May, when it won one of the biggest victories ever secured by the center-left in Italy.
The results will have no direct impact on the government or on Renzi's majority in parliament - his ambitious program of economic and institutional reforms will remain in place. But the electoral performances underline the turnaround in the party's fortunes since he took office in February as Italy's youngest prime minister in the face of resistance from many of his party's old guard.
The center-right, weakened by the legal problems facing former Prime Minister Silvio Berlusconi, now serving a community service sentence for tax fraud, had one significant victory in the town of Perugia, which it took from the PD.
But Berlusconi's Forza Italia party remains divided and uncertain in the face of both its own leader's weakness and the recent triumphs of the 39-year-old Renzi.
"The renewal of Forza Italia is indispensable," the former mayor of Pavia Alessandro Cattaneo, who lost the city despite his own high personal popularity, told RAI state television on Monday.
The run-off votes in dozens of towns and cities followed last month's European elections, in which Renzi won nearly 41 percent of the vote.
The 5-Star Movement, founded by former comedian Grillo and which had been hoping to improve on its stunning success in last year's parliamentary election, when it won 25 percent of the vote, instead saw its vote drop to around 21 percent while Forza Italia took just under 17 percent.
Sunday's run-off ballot was the last stage in a series of local elections in more than 4,000 towns across Italy, most of which ran concurrently with the May 25 European parliament vote.
(Reporting By James Mackenzie, additional reporting by Silvia Ognibene; Editing by Alexandra Hudson)