French presidential election candidate Emmanuel Macron delivers a speech Friday during an election campaign rally in Albi, France. (Frederic Scheiber/European Pressphoto Agency)

PARIS — On a warm spring afternoon, as the streets of this capital city buzzed with tension ahead of the fateful French election Sunday, quiet reigned inside the 12th-century parish church of Saint-Germain de Charonne.

The candles were lit, but the pews were mostly empty. A few people, mainly older women, came in alone to pray. One said religion was no longer so important to her, but she had “needs” she wanted to take to God.

Another said her Catholic faith was at the center of her life. Did it dictate how she would cast her vote Sunday?

“I wish,” was the answer.

France once did battle to defend Catholicism. Now it is home to one of the world’s largest populations of atheists. It is a country wrapped in its religious past yet proud of its commitment to secularism — or laïcité — in the present.

Whether this is a contradiction, and whether public displays of faith are compatible with France’s republican ideals, is a question of great import in the election here. The results will shape the West’s relationship to Islam. They could also decide the very future of Europe.

Yet the strict separation of church and state masks an underlying truth about a country where most people are Catholic, whether practicing or lapsed: Whom voters choose to support for France’s highest office is still influenced by religious fault lines.

“Religion continues to be a very important factor even though the country is secular,” said Bruno Cautrès, a political scientist at Sciences Po in Paris. “People without religion vote left. People with it vote right.”

In an election that has frustrated that traditional split, religion could end up being a confounding, rather than clarifying, force, like much else in a series of Western elections shattering long-standing political loyalties.

In France, religion offers a unique window into this uncertainty, given the absence from the final round on Sunday of Les Républicains, the center-right party traditionally favored by the country’s practicing Catholics. This throws open to question the allegiance of a sizable bloc of voters — those who helped François Fillon, the conservative standard-bearer felled by corruption and nepotism, eke out a third-place finish in the first round, with 20 percent of the vote.

Their decision now is whether to side with Emmanuel Macron, a political novice whose brand-new party, “En Marche!” (Onward), espouses liberal social views, or with Marine Le Pen, the leader of the far-right National Front who has moved the party away from hard-line social issues and toward strict economic nationalism.

Of course, they could also stay home.

Following a moment of prayer in the medieval church, Josette, a retiree who declined to give her last name because she believes political views should be private, said she voted for Fillon in the first round and now cannot make up her mind.

Neither can Gisele Duchaussoy, who used to work in accounting. She voted for the right-wing Union for a Popular Movement two weeks ago and finds the two remaining options equally unpalatable. She expects to vote blank.

Missing has been guidance from Catholic leaders, whose silence represents one more chink in the armor of the so-called “Republican Front,” the bipartisan coalition that has come together in previous contests to keep the National Front from power. Though Fillon was quick to endorse Macron, condemning the “extremism” of the far-right party, those with perhaps even greater sway over his most devout followers, French bishops, have not been as decisive.

This marks a change from 2002, when leading bishops spoke collectively against Le Pen’s father, Jean-Marie, when he shocked France by making it to the second round.

“What we have now is silence from the bishops,” said Jean-Dominique Durand, an expert on the history of contemporary Christianity and a deputy mayor of Lyon. “Protestants, Muslims, Jews have all mobilized for Macron. Not the Catholics, not in any clear way.”

A joint letter signed by the president of the Protestant Federation of France, the chief rabbi of France and the head of the French Council of the Muslim Faith said only that a vote for Macron guaranteed a “France confident in its future.”

But Georges Pontier, head of the Bishops’ Conference of France, defended the decision to stay above the fray in a post on the conference’s website, saying the church’s role, particularly in a “hysterical climate,” was not to “take sides” but “to remind each voter what our faith invites us to take into account.”

Certain bishops have weighed in against Le Pen, while others have given their congregations license to abstain. Powerful Catholic groups that helped Fillon mobilize his base have also declined to take a side. The head of Common Sense, a conservative Catholic network, told Christian Family magazine that it was impossible to choose between the “chaos” promised by Le Pen and the “political deterioration” represented by Macron.

Durand predicted that silence would be “catastrophic” for the church, undermining its credibility. It does not hesitate, he said, to take a stance on other volatile issues, such as same-sex marriage. And while the conference has not voiced disapproval of Macron, Durand said, its “silence is tantamount to saying that the two candidates are equal.”

In 2002, Catholic voters had a preferred alternative to the National Front, as Jacques Chirac, leader of Les Républicains, was Le Pen's rival in the second round. He was a safe bet for conservative Catholics. Many of these voters don't know what to make of Macron.

The 39-year-old former Socialist economy minister bears a unique relationship to Catholicism, though he rarely talks about his religious beliefs. Raised in a secular family, he chose to be baptized at the age of 12 before entering a Jesuit school in Amiens in Northern France. The school brought him “discipline of mind and a desire for openness to the world,” he said in an interview with La Vie, a weekly Roman Catholic magazine. Afterward, he practiced less, he said, but remains in “permanent reflection on the nature of my own faith.”

Durand, the religious historian, said Macron’s discourse is marked by Catholicism, even though he does not proclaim his faith, as did Fillon.

“He doesn’t say, ‘I am a Christian,’ but look at the words he uses — goodwill, benevolence, welcome — or the way he addresses people as ‘my friends,’ ” Durand said. “It’s a program that is marked by humanism and respect for others, particularly immigrants, and I think you could say this came from his education and from the social doctrine of the church.”

But with debates over the integration of Muslims playing out over matters of public dress and activity, a “typical liberal view of laïcité” may leave vulnerable citizens unprotected, said Sarah Wolff, an expert on European security and external relations at Queen Mary University of London. Macron, should he win the presidency, may have to take a more controversial stand, she said.

“What is needed is a critical approach to adapt laïcité to current times,” Wolff said. “Laïcité as equal conditions for all citizens to practice their religion.”