FOR the first time, both mainstream parties of the left and centre-right in France are holding primaries to select their nominees for next year’s presidential election. In the past, French parties tended to agree on candidates behind closed doors, or after a narrow vote among members. Sometimes, unresolved rivalry led candidates from the same political family to run anyway, splitting the vote. This time, a new system is in place. On November 20th and 27th, the centre-right Republicans hold their first election open to any supporter who pays €2 ($2.15) and signs a charter of centre-right values. The Socialist Party follows with its two-round primary on January 22nd and 29th.

The ostensible reason is the parties’ desire to be more modern, open, transparent and fair. The Socialists led the way in 2011, holding their first primary open to any voter. Nearly 3m people took part—seven times the number of voters who elected Jeremy Corbyn at the Labour Party leadership race in 2015. Last month, for the Republicans’ first televised debate, fully 5.6m viewers tuned in to watch the seven candidates. They include a former president, Nicolas Sarkozy, and two former prime ministers, Alain Juppé and François Fillon. The primary has done a good job of levelling out former rank, with candidates lined up behind identical lecterns in a debate studio, and allocated equal speaking time. Neither Mr Sarkozy, the Republican party leader, nor François Hollande, the sitting Socialist president, is guaranteed his party’s nomination.

In reality, though, a different factor explains France’s enthusiasm: Marine Le Pen, leader of the ultranationalist National Front. In the past, parties could afford to use the first round of a presidential election to filter rival candidates from the same party. This happened, for example, in 1995, when both Edouard Balladur and Jacques Chirac from the centre-right entered the race. Mr Balladur was eliminated in first-round voting, leaving Mr Chirac to go forward to the run-off against a Socialist, whom he beat. Today, Ms Le Pen’s position as favourite to win the first round in April 2017 means that the left and centre-right may be competing for a single place in the run-off against her. Neither party can risk division by fielding more than one candidate, especially as polls currently suggest that the Socialists would be eliminated.

The upshot is that France’s primary season is turning into a proxy first-round of the presidential election: a race to select the candidate best-placed to take on Ms Le Pen. The two front-running Republicans, Mr Juppé and Mr Sarkozy, offer quite different solutions. Mr Juppé, who rejects identity politics, would have greater appeal to voters on the left, if the Socialist candidate fails to make it through. Polls suggest he would beat Ms Le Pen by 68% to 32%. Mr Sarkozy, who has seized nationalist themes in a bid to reach FN voters, would rally fewer on the left, winning by just 58% to 42%. Before Donald Trump’s victory, such polls looked plausible and, it seemed, the next French president might be selected six months before the actual election. But this assumed that Ms Le Pen could not win. Now nothing seems quite so sure.