French diplomacy could be headed for an unprecedented period of turbulence if the far-right wins a snap parliamentary election, with President Emmanuel Macron and a potential National Rally (RN) prime minister jostling for the right to speak for France.
Marine Le Pen's anti-immigrant, eurosceptic RN extended its lead over Macron's centrist bloc, according to opinion polls published on Friday, the last day of campaigning before Sunday's first round of voting. A second round will take place on July 7.
Voters and diplomats alike have long been accustomed to the president calling the shots in foreign and security policy for France, a permanent member of the U.N. Security Council and a nuclear power, with one of Europe's most powerful militaries.
But what is known in France as the president's "reserved area" of defence and diplomacy is not explicitly stated in the constitution but is more a matter of convention, and this could spell trouble if the RN forms the next government.
During the three previous periods of "cohabitation" since 1958 - when the president and prime minister hail from different parties - tensions sometimes erupted but were quickly doused.
This time could prove more difficult, and Jordan Bardella, the 28-year old RN leader and likely next prime minister, has already indicated he would challenge Macron on global issues.
"It's going to be trench warfare," Gerard Petitpré, a French constitutional lawyer, told Reuters.
Even before the election, the battle lines are being drawn.
Macron told leaders from the European Union's liberal Renew grouping in Brussels on Thursday he would propose faithful ally Thierry Breton as France's commissioner in the next EU executive, a diplomatic source said on condition of anonymity.
That came after Bardella said he was considering other candidates for the job. Le Pen swiftly decried Macron's move.
"Emmanuel Macron is anticipating a victory he cannot win. So he won't be able to name Mr Breton," she told Europe 1 radio. "It is the prime minister's prerogative to name the European Commissioner."
'HONORARY TITLE'?
Experts say the French constitution, while awarding the president greater powers on foreign policy than in most parliamentary democracies, still leaves the main levers of policy in the prime minister's hands.
The president is commander-in-chief, chairs defence meetings, negotiates international treaties, and is ultimately the only person able to order the use of France's nuclear deterrent.
But the prime minister heads France's administration and controls the state budget, which must be approved by parliament.
That prompted Le Pen to say the president's title of commander in chief was "honorary", causing outrage in Macron's camp.
"It's an honorary title because the prime minister holds the purse strings," she said.
"Jordan does not intend to pick a fight with him but he has set red lines. On Ukraine, the president will not be able to send troops," she added, referring to Macron's refusal to rule out the possibility of sending French troops to Ukraine.
French constitution expert Petitpré said Le Pen was within her rights to interpret the founding charter that way, but that it could ultimately come back to haunt her, as a president has various ways of making a government's life difficult.
"She shot herself in the foot by signalling they would go for a hard cohabitation," he said. "The president has extensive powers to resist and he will now know he has to use them."
Petitpré cited the first cohabitation period in 1986, when Socialist Francois Mitterrand refused to accept the foreign and defence ministers proposed by conservative prime minister Jacques Chirac because they had virulently criticised the president. Chirac eventually had to propose two different names.
STRANGE DUEL
Past cohabitations made for some incongruous scenes at global gatherings. Chirac insisted on attending the 1986 G-7 summit in Tokyo along with Mitterrand, irritating the president who nonetheless managed to be the only one to speak at the final press conference.
By the time of a European summit later that year, the two men had managed to agree a common position even on divisive issues such as South African apartheid.
Under a second cohabitation in 1994, the president and prime minister of the time agreed on sending troops to Rwanda. The third and most recent cohabitation - with Chirac as president and Socialist Lionel Jospin as premier - also went relatively smoothly in foreign policy, with only a few disagreements.
The French would be unforgiving towards leaders who exposed their divisions on the global stage so both sides would have an interest in avoiding overt hostility, said law professor Anne-Marie Cohendet from Paris Pantheon-Sorbonne university.
"Specialists say cohabitation is a strange duel in which the one who shoots first is dead," she said.
However, past cohabitations were between leaders from mainstream parties who largely agreed on major foreign policy issues and the importance of France's alliances.
The RN, which has never held power, has made no secret of its disdain for EU institutions, and has said it wants France to leave NATO's integrated command, though not while the war in Ukraine is raging.
"Should there be a cohabitation between Emmanuel Macron and the RN, it would be nothing like the previous ones... and would be very tough," a former minister who experienced a cohabitation period told Reuters on condition of anonymity.
