ROME — Italian Prime Minister Giuseppe Conte found himself this week offering an increasingly familiar reassurance. No, he said, Italy’s fractious two-party coalition is not on the verge of collapse.

For the past nine months, Italy’s two governing parties have clashed over everything from migration policy to budget small-print to waste incinerators. This week it was a planned rail link through the Alps that highlighted the conflict, forcing Conte to mediate still-unresolved talks.

“The government is not at risk,” he said once more.

This is the delicate union at the center of Italy’s political landscape, where two very different parties — the far-right League and the politically amorphous Five Star Movement — are joined in determining the fate of Western Europe’s first fully populist government.

Italian newspapers document the tensions almost daily. Some analysts predict the coalition won’t last beyond the spring.

Others say the two parties, despite policy clashes, share an anti-establishment DNA — and have reason to stick with each other in a country where voters en masse have turned away from the political status quo. If either party pulled the plug on the relationship, it would need the help of less popular old-guard parties to win new elections. Meanwhile, the current government is reasonably popular, with an approval rating above 50 percent.

“This is not a marriage of love. It is a marriage of convenience,” said Roberto D’Alimonte, a political science professor at Luiss Guido Carli University in Rome. “Sometimes marriages of convenience are more lasting.”

Though the relationship has held, some pundits say tensions have increased because one party, the League, is clearly outpacing the other. Led by Matteo Salvini, the League last year entered the coalition as the smaller and less popular party. But it has soared in the polls and now claims support from some 36 percent of Italian voters, as opposed to 21 percent for the Five Star Movement. The League recently trounced the Five Star Movement in several recent regional elections.

Some Five Star members say the party has been outmaneuvered and overshadowed by Salvini, a tireless social media promoter who is the architect of Italy’s hard-line anti-migration policies. Salvini holds the title of interior minister, but he is widely viewed by Italians as the nation’s de facto leader.

“For how long will the Five Stars take it?” said Ilvo Diamanti, a professor of political science at universities in Paris and Urbino, Italy. “Poll numbers are one thing. But when you end up being wiped out in the two regions where they [recently] had a vote, problems manifest more clearly.”

The two parties are both skeptical of European integration — though they have backed away from earlier wishes to withdraw from the euro zone. Both also have advocated for closer ties with Russia.

In other ways, the parties are different — and have distinct visions for what populism should look like. The Five Star Movement draws its support from the impoverished south, the League from the industrial north. The Five Star Movement has advocated for Internet-based direct democracy. The League emphasizes “Italians First” nationalism with restrictions on migrants coming to Italian shores.

The parties have managed to cooperate on economic measures — important in a country with two decades of stagnation. But their different prescriptions — the League has called for tax cuts, the Five Stars want expanded welfare benefits — threaten to stretch the country’s budget.

The parties are running against each other in European parliament elections in May.

Members of the Italian political class anticipate the government will be more vulnerable after those elections. If the Five Star party takes a beating, party leader and Deputy Prime Minister Luigi Di Maio will face internal pressure to rethink his strategy.

And if his popularity continues to climb, Salvini might be tempted to call for a new election in Italy and try to become prime minister.

Given that uncertainty, the high-speed rail project, known as the TAV, has become one more significant arm-wrestling match for which party’s priorities will win out. Five Star members have portrayed the rail line as an environmentally damaging and needless expenditure, especially in a nation where other infrastructure projects may be more pressing. But the northern business class that supports the League favors the project, and Salvini has pushed for the Turin-to-Lyon rail link to go ahead. Conte has indicated the government will decide on the project by Friday.

Massimo Franco, a columnist at the Corriere della Sera newspaper, said Salvini and Di Maio seem to have a firm personal relationship. When they have faced decisions that could backfire on either of them, they have used Conte — a compromise choice for prime minister — as a figure who can absorb some of the criticism.

“Every time there is a difficult situation, they make it look like he is the one who decides,” Franco said.

Recently, the Five Star Movement faced a difficult decision of its own — and ended up offering Salvini a helping hand.

Salvini was one step away from facing trial on kidnapping charges related to his effort last year to block a coast guard boat with more than 150 migrants aboard from returning to Italian shores. Salvini, as a minister, had immunity from prosecution, unless a parliament committee voted to lift it.

Legal protection for a government minister, analysts said, was exactly the thing Five Star members would have railed against in earlier years. This time, however, Di Maio and another Five Star minister wrote a letter approving of Salvini’s actions. Last month, the party put the decision to an online vote, asking its supporters whether Salvini was entitled to immunity. Some 59 percent said he was. Soon after, a parliamentary group took up the matter, and every Five Star committee member voted to maintain Salvini’s protection.

“We’re a team,” Salvini said afterward. “There is a team at the helm of the government. I thank the team for the trust.”

Stefano Pitrelli contributed to this report.