With just days to go before the first round of the election, nearly a third of French voters still haven’t decided which candidate they’ll pick — or even whether they’ll go to the polls.

Voter indecision “is enormous,” said Gaël Sliman, head of polling group Odoxa.

In what is turning into one of the most unpredictable elections in recent French history, undecided and no-show voters could upend a race in which the four top contenders are clustered within a few points of each other. With each polling at about 20 percent for the first round on April 23, the two candidates for the runoff may be determined by people who have yet to make up their minds.

An Odoxa survey for France Info, released April 14, puts the undecided rate at 32 percent. The percentage of voters saying they’re sure of their choice is the lowest since 2002, when the far-right National Front pulled off an upset in the first round of presidential voting, Emmanuel Riviere, a pollster at Kantar Sofres, said on his Twitter feed on April 12. “Indecision remains high, as in 2002,” he said.

Adding to the uncertainty, only 66 percent of eligible voters are relatively certain they’ll cast their ballots, according to an April 14 poll by Ipsos Sopria-Steria for Le Monde. That’s well below the 79.5 percent turnout in the first round of the 2012 presidential election.

An OpinionWay poll published today, showed the far-right National Front’s Marine Le Pen tied with centrist Emmanuel Macron at 22 percent each, followed by center-right Republican François Fillon at 21 percent and Communist-backed Jean-Luc Melenchon at 18 percent. The poll shows both Macron and Fillon beating Le Pen easily in the May 7 runoff.

Melenchon’s Support

Support for Melenchon looks particularly soft. While he has surged in the polls after strong performances in recent debates, Odoxa’s survey found that 34 percent of voters who listed him as their first choice said they might still change their minds. The comparable figure for Macron was 23 percent, while 20 percent of Fillon’s probable voters and 13 percent of Le Pen’s said they still could switch.

Melenchon and Le Pen also could have trouble getting their voters to the polls. The Ipsos survey found that only 65 percent of far-left supporters and 68 percent of National Front supporters were likely to vote on April 23. By contrast, 75 percent of those backing Macron’s independent On The Move! party, 74 percent of Republicans, and 72 percent of Socialists said they expected to vote.

Many voters who supported President François Hollande in 2012 “are disappointed in the government’s performance, and decided to stay at home,” said Douglas Webber, a political science professor at the Insead business school in Fontainebleau.

Voter Discontent

In another sign of voter discontent, both of the country’s establishment parties risk having their candidates eliminated in the first round. Socialist nominee Benoit Hamon has slid to fifth place with only 8 percent in the latest OpinionWay poll, while Republican Fillon is in third place after his support crumbled over allegations that he used public funds to hire his wife for fake jobs.

The centrist Macron has picked up support from some Socialists and Republicans, but ordinary voters “don’t really know him,” said Françoise Falcy, a retired phone worker shopping at an open-air market in the Paris suburb of Sartrouville. Falcy said she was considering Macron after being disillusioned by Fillon.

The potential for last-minute switching appears greatest among Socialist voters. Odoxa’s poll, conducted April 12 and 13, found that 43 percent of them still were undecided, compared with 29 percent of center-right voters, 26 percent of far-left supporters, and only 7 percent of National Front supporters.

Advantage Macron

The candidate who could benefit most may be Macron.

He is “the best catch-all politician of all who are running,” Antonio Barroso, deputy director of research at Teneo Intelligence in London, wrote in an April 12 note to clients.

Still, the pool of undecided voters is large enough to give each of the four leading candidates a shot at reaching the second round, Odoxa’s Sliman said.

For example, some 17 percent of likely voters told Odoxa they still hadn’t made up their minds between Melenchon and Macron. If most of them went for Melenchon, that would vault him from fourth to first place. The third-place Fillon could pull off a similar upset if he could attract the 10 percent of voters who say they might vote either for him or Macron.

The last big upset in French presidential voting was in 2002, when Le Pen’s father, National Front founder Jean-Marie Le Pen, beat the Socialist nominee in the first round. However, he lost the runoff in a landslide to then-President Jacques Chirac.

This time, Webber said, “the outcome is less predictable.”