Mr. Gentiloni took power after Matteo Renzi, the party’s charismatic 42-year-old leader, quit in the wake of a stinging defeat in a national referendum to change the Constitution in ways he hoped would make Italy’s notoriously volatile politics more stable. Mr. Renzi had previously ousted Enrico Letta in a political maneuver.
Over the months, the governing majority has fractured, with more than 300 lawmakers abandoning the Democratic Party, leading to a perennial search for consensus within the Parliament.
Speaking with reporters at a traditional year-end news conference, Mr. Gentiloni admitted on Thursday that he had survived a “troubled” tenure and said that he hoped that the campaign would not be influenced by “merchants of fear and illusions.”
Italy, like other countries, including the United States, is now wary of the sudden, unpredictable influences of internet propaganda amplified by the abundant audience of social media.
The country’s general election will be the next test of an important European nation that hopes to ward off potential outside meddling, bogus news stories and populist forces.
With voting now just a little more than two months away, both the anti-establishment Five Star Movement and the far-right League party have been steadily gaining in opinion polls.
Mr. Gentiloni, the country’s 28th prime minister since 1946, acknowledged that Italy was not unfamiliar with political turmoil and government changes, yet he insisted that the risk of instability could be managed.
“I think we are vaccinated,” he joked, though he added a serious note of warning against the risks of amateur politicians, in a jab at the relatively new Five Star Movement.
That inoculation comes in the form of a new electoral law devised to favor broad coalitions that was approved last fall, after years of political debate and months of parliamentary wrangling.
Yet the new legislation has already proved controversial. Many observers have criticized the law for falling short of the stability its supporters had promised.
In particular, the Five Star Movement has protested that the law was intended as a bulwark by Italy’s political establishment to prevent it from taking power.
The Five Star Movement — a pro-Russian, conspiracy-prone, insurgent agglomeration that prides itself on using nonprofessional politicians — enters the campaign as Italy’s most popular political force.
The movement, one of whose founders was the comedian Beppe Grillo, has already chosen its candidate for prime minister: Luigi Di Maio, 31, who has served as vice president of Italy’s lower house of Parliament.
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But the party insists that it will refuse alliances with traditional parties. Unless it changes its stance, it would appear for now to have a slim chance of gaining power under the new voting system, which favors coalitions and established parties.
The Five Star Movement could nonetheless shape much of the campaign debate, and help push other candidates to the right.
That shift has been helped, too, by Mr. Berlusconi, a four-time prime minister, who recently enlivened the conservative end of the political spectrum with yet another comeback.
He has appeared on television shows and on social media sites, promising to slash taxes and overhaul immigration policies.
Because he has been convicted of fraud, Mr. Berlusconi is ineligible to serve again as prime minister. But his Forza Italia party may be poised to strike a deal with the anti-immigration League, a right-wing party led by Matteo Salvini that is polling at 12 percent.
The governing Democratic Party is currently favored by about 22 percent of the electorate — a level of support that a coalition of right-wing parties could easily surpass.
“Mr. Gentiloni created stability and relative credibility abroad, but our fellow European countries keep looking at us with concern,” said Gianfranco Pasquino, a professor emeritus of political science at the University of Bologna and a senior adjunct professor at the Bologna Center of the Johns Hopkins University’s School of Advanced International Studies.
“And with this electoral law, it will be difficult to have a cohesive enough majority,” Mr. Pasquino said.
On Thursday, Mr. Gentiloni called his tenure “fruitful,” saying that he had steered lawmakers to pass a budget without major tax increases, contributed to Italy’s economic recovery and reduced the number of migrants reaching Italian shores.
Still, immigration is likely to remain one of the most divisive issues of the campaign.
Mr. Gentiloni’s government’s had tried to naturalize an estimated 800,000 children who were either born in Italy to foreign parents or had arrived at a young age. Foreigners born in Italy can currently apply for citizenship only when they turn 18 and if they have lived in the country since birth.
But Mr. Gentiloni was unable to get enough senators to push through the changes he sought to the citizenship laws so the effort was set aside until next year.
Many lawmakers feared a political blowback if they approved a bill that was largely opposed by right-wing parties and not endorsed by the Five Star Movement.
“Mr. Gentiloni was attentive in avoiding reasons for division, and he succeeded,” Sergio Fabbrini, a political analyst and the director of the School of Government at Luiss Guido Carli University in Rome. “He is a politician of mediation, not one of confrontation.”
Despite Italy’s penchant for flamboyant and mesmerizing leaders, recent polls have found that the tranquil Mr. Gentiloni is Italy’s most popular politician.
Even so, he is not likely to be a candidate for prime minister in the next elections, lacking the charisma of politicians with more of an edge, like Mr. Renzi.
But Mr. Gentiloni could still be asked to stay on by the president, if the elections produce a hung Parliament and no clear majority.