PARIS — Marine Le Pen is unlikely to become France’s next president even if large numbers of voters switch to her or abstain in the runoff, data from the presidential election’s first round suggest.

The far-right leader came in second on Sunday, and will face winner Emmanuel Macron, the centrist former economy minister, in the decisive second round on May 7.

Le Pen received almost 7.7 million votes, or 21.3 percent, to Macron’s 8.6 million (24 percent) according to the interior ministry’s final results.

To win the second round and be elected president, she needs 50 percent of valid votes plus one. In the first round, 35.5 million valid votes were cast, and overall turnout was just under 78 percent. So if turnout is the same in the second round, Le Pen would need more than 18 million votes to make it to the Elysée palace — 10 million more than her first-round total.

Both the politics and electoral arithmetic are stacked against her.

First, the politics. All the main candidates knocked out in the first round — except far-left upstart Jean-Luc Mélenchon, who came fourth with 19.6 percent — have explicitly called on their voters to switch to Macron. François Fillon, the third-placed conservative candidate, told sympathizers that “nothing would be worse” than voting for the far right. Socialist Benoît Hamon did the same Sunday night, and the Socialist Party’s ruling body followed suit on Monday by “unanimously” endorsing Macron.

The question is not so much whether Le Pen will win but what she could claim as a political victory.

So Le Pen would need large numbers of voters who supported those candidates to ignore their instructions and vote for her instead of Macron. Yet a simple calculation shows she wouldn’t get anywhere near her target even under scenarios that are, for her, highly optimistic.

Let’s assume Le Pen keeps all of the 7.7 million who voted for her in the first round, which is reasonable. Let's also assume the same turnout as in the first round. Then let's assume that:

45 percent of Fillon voters switch to Le Pen (pollsters expect that proportion to be in the 35-40 percent range)

20 percent of Mélenchon voters also back her (which seems unlikely)

20 percent of Hamon’s Socialist voters choose her (nearly impossible)

90 percent of the vote of another far-right candidate, Nicolas Dupont-Aignan, goes to her

Even then, the National Front leader would still fall more than 3.7 million votes short of the required majority.

Low turnout could help Le Pen

Le Pen's numbers, however, would improve if a larger part of voters decided to stay home. In that case, the number of votes she needs to win a majority would be lower.

Considering the Fillon electorate’s hostility towards Macron, and the relentless campaign that both candidates from the left have waged against the former economy minister in recent months, it is safe to assume that quite a few of their voters will prefer not to go to the polls. Or, if they do get to the voting booth, they could submit invalid ballots as a way of showing their rejection of both candidates.

But, again, even under a rosy scenario for Le Pen, abstentions and spoiled ballots do not get her close to victory. Let's assume the same defections to Le Pen from other candidates' supporters outlined above. Then let's also suppose:

Invalid ballots account for 5 percent of the vote in the second round (double the percentage from round one)

30 percent of Fillon’s, 30 percent of Mélenchon’s and 20 percent of Hamon’s voters don’t go to the polls

All the 626,000 voters who went for two fringe Trotskyite candidates abstain too

Even then, Le Pen would fall short by about 635,000 votes. And note that the turnout, at just 67 percent, would be at a historical low for a presidential contest — even lower than in 1969, when the left, then dominated by the Communist Party, chose en masse abstention because the two final candidates both hailed from the center right.

Looking at the electoral arithmetic, the question then is not so much whether Le Pen will win but what she could claim as a political victory even while going down to defeat. It’s safe to assume that anything much below 40 percent of the final tally — roughly the score pollsters currently predict — would look like a poor performance.

Under the most favorable scenario envisaged here, Le Pen would get 47 percent of the vote. That might be considered a level she could truly call a political victory. And it could make her the real leader of the opposition to President Macron for the next five years.