Mujtaba Rahman is the head of Eurasia Group’s Europe practice. He tweets at @Mij_Europe.

Few prime ministers in French history have entered office so exposed to the risk of instant rejection and calamitous failure as Sébastien Lecornu.

President Emmanuel Macron’s latest prime minister has inherited the twin problems of a ballooning deficit and a splintered National Assembly, which have combined to defeat two very experienced 70-something politicians, François Bayrou and Michel Barnier, in the last 10 months.

Lecornu has no experience at the highest levels of government. And though he’s had a meteoric rise since transitioning from the center right to join Macron’s promised “revolution of the center” eight years ago, he remains largely unknown to the French public. Still, throughout his tenure as junior environment minister and then defense minister, he’s grown closer to Macron than any of the other prime ministers or senior ministers in the six governments that have come and gone since 2017.

Lecornu now has less than two weeks to shape the broad outlines of a deficit-cutting deal with the Socialist swing group in the National Assembly, and one month before he has to present detailed plans for a 2026 budget to parliament on Oct. 13. But Macron himself has given the new prime minister an even tighter deadline: The principles of a budget deal must be agreed on before any ministerial posts are allotted upon the president’s return from the U.N. General Assembly on Sept. 24.

The problem is, if and when a broad approach is settled on, detailed negotiations with the Socialists on the deficit-cutting budget could go on for quite some time — and Lecornu’s government may not survive beyond the end of next month.

The Socialists, whose 66 votes in the assembly control the prime minister’s fate, say they want an early promise that he’ll radically change course from his predecessor Bayrou, who was planning to reduce the deficit by €44 billion next year. Rather, they want a deficit cut of no more than €22 billion, mainly achieved via a new mechanism for taxing the “super rich.” And even more problematic, they’re insisting the new government suspend Macron’s controversial 2023 pension reform.

Lecornu has already signaled his willingness to make concessions, telling the French regional press over the weekend that Bayrou’s plan to abolish two public holidays in order to raise €4 billion will be abandoned. As will the previous prime minister’s plan to reduce the deficit to 4.6 percent of GDP next year (from an expected 5.4 percent of GDP this year).

Instead, the Lecornu government wants to hold out for a cut to around 4.8 percent of GDP — though the Socialists say a reduction to 5 percent is all the country can sustain. Moreover, they’re demanding there be no freeze in social spending, as well as increased budgets for education and health.

The Socialists also claim, rather improbably, that almost all the deficit savings can be achieved via their new proposed wealth tax. And though Lecornu’s government is ready to accept a less draconian wealth tax, which would be levied only on noncommercial assets, the center-right part of the minority coalition warns that any large tax hikes might breach their redlines.

Most worryingly for Lecornu, though, Socialist leaders have again decided to raise the thorny issue of pension reform. And they say there can be no deal unless the new prime minister suspends the progressive increase of France’s official retirement age from 62 to 64, which was imposed by special government powers in 2023.

Such a demand would be a deal-breaker. Pension reform is one of the few accomplishments of Macron’s second term. It’s also one of the few deficit-reducing measures passed in recent years — reversing or suspending it would undermine any remaining market confidence in France’s ability to confront its debt problem.

And though the government may offer some kind of revision of the overhaul, improving the terms for women and manual laborers, that may not be enough to secure a non-aggression or non-censure pact with all 66 Socialist deputies — which Lecornu needs to survive.

Ultimately, Lecornu is gambling on the Socialists’ fear of an early parliamentary election — something that would become very likely if another prime minister were to fall. But some Socialists, however, say their real fear is making a deal with an unpopular government, which would wreck the party’s chances of holding onto big cities, including Paris, in next year’s municipal elections.

Now, Lecornu must find a narrow path between these maximalist Socialist demands for taxing the wealthy and the anti-tax redlines drawn by his center-right coalition partners. If he fails to navigate a route through this minefield, he’ll be leading France into truly uncharted territory.