BRUSSELS — Italy’s likely new prime minister, the far-right, populist and Euroskeptic Giorgia Meloni, once wanted to ditch the euro currency and blasted Italy for “surrendering to the bureaucrats in Brussels” by adhering to European spending rules.

Ms. Meloni, who would be the first far-right nationalist to govern Italy since Mussolini, says that she has moderated her views. But European leaders wonder if she is dissimulating, and the European Union is watching her coalition’s comfortable victory in Italy, one of its founding members, with caution and some trepidation.

Not least, Brussels is worried that despite the bloc’s successes in recent years in coming together for a groundbreaking pandemic recovery fund and to confront Russia’s aggression in Ukraine, the appeal of nationalists and populists remains strong — and is spreading.

Ms. Meloni’s victory signals a new right-wing shift in Europe, following on the heels of the strong showing of the far-right Sweden Democrats this month, when they became the country’s second-largest party and the largest in what is expected to be a right-wing coalition.

The economic impact of Covid and now of the war in Ukraine, with high national debt and rocketing inflation, has deeply damaged centrist parties all over Europe. Far-right parties have not only pushed centrist parties to the right, but have also become “normalized,” no longer ostracized, said Charles A. Kupchan, a European expert at the Council on Foreign Relations.

“The direction of political momentum is changing — we had a wave of centrism before and during the pandemic, but now it feels like the political table is tilting back in the direction of the populists on the right,” he said. “And that’s a big deal.”

Under the outgoing technocratic prime minister Mario Draghi, Italy played an important role in a Europe of weak leadership, both on vital economic issues and the response to Russia’s invasion of Ukraine. But Italy has now turned away from the European mainstream.

An Italy led by Ms. Meloni is likely to be constrained by European control over billions of euros in crucial funding. In the best case, diplomats and analysts say, it will not smash the European consensus, but could severely complicate policymaking.

If Ms. Meloni and her coalition partners choose to side with other populist, Euroskeptic leaders inside the European Union, like Prime Minister Viktor Orban of Hungary and Prime Minister Mateusz Morawiecki of Poland, she can certainly “gum up the works,” Mr. Kupchan said.

For Italy to team up with “Orban and company is Brussels’ nightmare,” said Stefano Stefanini, an analyst and former Italian diplomat. “For over 10 years the E.U. has lived with the fear of being swamped by a tide of Euroskeptic populism,” he said. “Hungary is a pain, but Italy joining forces with Hungary and Poland would be a serious challenge to the mainstream E.U. and would mobilize the far right in other countries.”

The first European congratulations to her came Sunday night from Hungary. Mr. Orban’s political director, Balazs Orban, said in a Twitter message: “In these difficult times, we need more than ever friends who share a common vision and approach to Europe’s challenges.”

Europe’s concerns are less about policy toward Ukraine. Ms. Meloni has said she supports NATO and Ukraine and has no great warmth for President Vladimir V. Putin of Russia, as her junior coalition partners, Matteo Salvini and Silvio Berlusconi, have evinced.

Still, Mr. Berlusconi said last week that Mr. Putin “was pushed by the Russian population, by his party, by his ministers to invent this special operation.” The plan, he said, was for Russian troops to enter “in a week to replace Zelensky’s government with a government of decent people.”

Italian popular opinion is traditionally sympathetic toward Moscow, with about a third of seats in the new Parliament going to parties with an ambiguous stance on Russia, sanctions, and military aid to Ukraine. As the war proceeds, with all its domestic economic costs, Ms. Meloni may take a less firm view than Mr. Draghi has.

Mr. Kupchan expects “the balance of power in Europe will tilt more toward diplomacy and a bit less toward continuing the fight.” That is a view more popular with the populist right than with parties in the mainstream, but it has prominent adherents in Germany and France, too.

“These elections are another sign that all is not well with mainstream parties,” said Mark Leonard, director of the European Council on Foreign Relations, and spell a complicated period for the European Union.

Even the victory a year ago of Olaf Scholz in Germany, a man of the center left, was ensured by the collapse of the center-right Christian Democrats, who had their worst showing in their history, while in April, France’s long-dominant center-right Republicans fell to under 5 percent of the vote.

“People in Brussels are extremely anxious about Meloni becoming an E.U. prime minister,” Mr. Leonard said. “They’ve seen how disruptive Orban can be from a small country with no systemic role in the E.U. Meloni says she won’t immediately upend the consensus on Ukraine, but she could be a force for a much more virulent form of Euroskepticism in council meetings.”

One or two troublemakers can do a lot of a damage to E.U. decision-making, he said, “but if it’s five or six,” it becomes very hard to obtain coherence or consensus.

When the leftist, populist Five Star Movement led Italy from 2018 to early 2021, before Mr. Draghi, it created major fights inside Brussels on immigration and asylum issues. Ms. Meloni is expected to concentrate on topics like immigration, identity issues (she despises what she calls “woke ideology”), and future E.U. rules covering debt and fiscal discipline, to replace the outdated growth and stability pact.

But analysts think she will pick her fights carefully, given Italy’s debt mountain — over 150 percent of gross domestic product — and the large sums that Brussels has promised Rome as part of the Covid recovery fund. For this year, the amount is 19 billion euros, or about $18.4 billion, nearly 1 percent of Italy’s G.D.P., said Mujtaba Rahman, Europe director for the Eurasia Group, with a total over the next few years of some 10.5 percent of G.D.P.

“Draghi has already implemented tough reforms to satisfy Brussels, so there is no reason for her to come in and mess it up and agitate the market,” Mr. Rahman said. But for the future, there are worries that she will push for an expansionist budget, looser fiscal rules and thereby make the more frugal countries of northern Europe less willing to compromise.

For Mr. Rahman, the bigger risk for Europe is the loss of influence Italy exercised under Mr. Draghi. He and President Emmanuel Macron of France, “were beginning to create an alternative axis to compete with the vacuum of leadership now in Germany, and all that will be lost,” Mr. Rahman said. Italy will go from a country that leads to one that Europe watches anxiously, he said.

There was a sign of that anxiety just before the election, when Ursula von der Leyen, the president of the European Commission, warned that Brussels had “the tools” to deal with Italy if things went in a “difficult direction.” It was seen as a hint that the European Commission could cut funds to Italy if it were deemed to be violating the bloc’s democratic standards.

Mr. Salvini, seeing an opportunity, immediately responded: “What is this, a threat? This is shameful arrogance,” and asked Ms. von der Leyen to “respect the free, democratic and sovereign vote of the Italian people” and resist “institutional bullying.”

Instead, Mr. Stefanini, the former diplomat, urged Brussels to be patient and to engage with Ms. Meloni. “The new government should be judged on facts, on what it does when in power,” he said. “The real risk is that by exaggerated overreactions the E.U. makes legitimate concerns self-fulfilling prophecies.

“If she’s made to feel rejected, she’ll be pushed into a corner — where she’ll find Orban and other soulmates waiting for her, and she’ll team up with them,” he continued. “But if she’s greeted as a legitimate leader, democratically elected, it will be possible for the E.U. to do business with her.”

Luuk van Middelaar, a historian of the bloc, also urges caution. European leaders know two things about Italian prime ministers, he said. First, “they are not very powerful at home, and two, they tend not to last very long” — since World War II, an average of about 18 months.

“So they will wait and see and not be blown away,” Mr. van Middelaar said. If she lasts longer, however, she could energize other far-right Euroskeptics in other big countries like France, he said, “and that would make a real difference.”