What is a French prime minister’s job anyway?

PARIS — Former Brexit negotiator and European Commissioner Michel Barnier has been appointed as France’s next prime minister.
But France already has Emmanuel Macron as its president. So what exactly does a French prime minister do?
Unlike in the United Kingdom and Italy, where the prime minister is both nominally head of government and clearly runs the show, things in France are more complex.
Both the prime minister and the president of the Republic hold executive power in the French political system. But there is a reason why the names and the faces of French presidents are famous worldwide while the profile of French prime ministers usually doesn’t extend past the country’s borders.
The prime minister and his ministers are in charge of the day-to-day politics, they table laws in the parliament and implement them. It’s up to the prime minister, not the president, to defend the government’s priorities in parliament, to work out compromises with other political forces and settle potential divergences between ministries.
The president, who is directly elected in a separate election, holds more big-picture responsibilities: He usually represents France on the international stage, chairs council of ministers’ meetings, is the chief of the French army. He also has the power to dissolve the parliament, signs off on government decrees and to appoint the prime minister.
In this “two-headed” system, as constitutionalists sometimes call it, the balance of power between the president and the prime minister varies depending on the wider context of French politics at any given moment and who actually holds each office — especially if they are not from the same political camp.
If the president and the prime minister are allies, the president has a bigger role and the prime minister is more of a loyal soldier charged with executing a legislative agenda. That was, for instance, the case under the outgoing government led by Gabriel Attal, Macron’s longtime pupil.
Things work very differently when the president and the prime minister are political opponents, a situation known in France as cohabitation, in which the president is obliged to appoint a rival as prime minister if his party loses a legislative election.
In that case, the prime minister can make full use of his powers, with the president almost relegated to an honorific role, except for foreign and military duties.
Cohabitation is not unprecedented, with France being subjected to it three times since the birth of the Fifth Republic in 1958. Conservative Prime Ministers Jacques Chirac and Édouard Balladur worked with Socialist President François Mitterrand in the 1980s and 1990s, while Socialist Prime Minister Lionel Jospin cohabited with Chirac as president from 1997 to 2002.
Not really. It’s even more complicated this time around: In previous cohabitations, prime ministers always had an absolute majority in the parliament.
But Macron’s decision to dissolve parliament and call a snap election this summer left France’s National Assembly fragmented. The left-wing New Popular Front alliance won the most seats but none of the opposition parties won an absolute majority, leading to a hung parliament with three big blocs.
The New Popular Front claimed that its victory gave it the right to put forward a candidate for prime minister and tapped 37-year-old civil servant Lucie Castets for the post. Macron, however, refused to nominate her, arguing that she was not in a position to govern with stability. He instead opted for Barnier, who appears to have the backing of the centrists, the right-wing Les Républicains and — for now — tacit support from the far right.
Barnier’s appointment is uncharted political territory. He is neither a politician from Macron’s camp nor a fierce rival of the French president. The power dynamics between the two, and the effective role of the prime minister, are still to be seen. 
The French president usually represents France at the European Union and at European Council meetings, though during cohabitation prime ministers have attended some meetings.
But the prime minister is in charge of directing the government action also when it comes to EU files. The prime minister has the final word on divergences between different ministries on EU files. The so-called General Secretariat for European Affairs is placed under his authority: Its task is to find an agreement between different ministries and finalize the French position before it is sent to French diplomats in Brussels.
Barnier may be more active than your typical prime minister thanks to the relationships and reputation he developed in Brussels as a former European commissioner and the bloc’s lead Brexit negotiator. That experience could prove to be an asset, as France is negotiating a plan with the Commission to cut its massive debt and avoid EU fines.