PARIS — Partial results in France's conservative presidential primary showed former Prime Minister Francois Fillon strongly leading Sunday over a moderate rival who accused Fillon of pandering to anti-immigrant, anti-Muslim populism.

Based on results from about 46 percent of polling stations, organizers of the Republicans party primary said Fillon had 68.5 percent of votes and Alain Juppe had 31.5 percent after their nationwide runoff election.

Polls had suggested Fillon was the front-runner after a surprise recent surge in popularity. However, it was the first time the party held a primary, making the early results inconclusive.

Fillon, 62, campaigned on promises of drastic free-market reforms, a crackdown on immigration and Islamic extremism, support for traditional family values and friendlier ties with Russian President Vladimir Putin.

Juppe, 71, had similar ideas on the economy, but had tried to rally conservatives around a more tolerant attitude toward France's ethnic, religious and social diversity.

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Polls suggest the winner of Sunday's primary runoff has a high chance of winning the French presidency in the April-May election — but would face a tough challenge from far-right leader Marine Le Pen.

Le Pen is banking on an anti-establishment campaign that particularly targets immigrants, France's large Muslim majority, and the European Union.

Le Pen is running an anti-establishment campaign that particularly targets immigrants, France's large Muslim majority, and the European Union.

Socialist President Francois Hollande is expected to announce in the coming weeks whether he will seek re-election, but the French left has been deeply weakened by Hollande's extreme unpopularity.

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Both Fillon and Juppe are high-profile leaders of the center-right Republicans party who knocked their former boss — ex-President Nicolas Sarkozy — out of the primary's first round of voting a week ago. Sarkozy threw his weight behind Fillon for the runoff.

Juppe, the perceived underdog, remained confident of victory after casting his second-round ballot in Bordeaux Sunday morning, despite finishing behind Fillon by double digits in the first round.

"I have no regrets. I ran a great campaign... I've defended my ideas until the end and it's going to work. I'm sure of it," Juppe told reporters. But he also acknowledged he had contemplated defeat.

Sunday's runoff comes after a bruising and highly adversarial end phase to the months-long primary contest, an American-style effort to end party infighting and bolster support for the party's nominee. The conservatives previously chose their candidate internally.

Fillon, a conservative Catholic who opposed France's law legalizing same-sex marriages, said he plans to reduce immigration to France "to a minimum" — positioning himself firmly to Juppe's right.

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He and Juppe also have strongly different views on how to deal with Russia, with Fillon in favor of forging closer ties.

He wants to drop sanctions against Russia over its aggressive actions in Ukraine and partner with Russia in the fight against Islamic State extremists.

Fillon insists "Russia poses no threat" to the West, while Juppe wants France to continue putting pressure on Putin on various fronts.

They both pledged to cut public spending, reduce the number of civil servants, raise the retirement age from 62 to 65, end the 35-hour work week and cut business taxes.

Fillon was the prime minister from 2007 to 2012 under President Nicolas Sarkozy, who was eliminated in the primary's first round a week ago and now is backing Fillon. Juppe was prime minister from 1995 to 1997 under President Jacques Chirac.

In the first round of primary voting on Nov. 20, Fillon won 44.1 percent of the votes, Juppe 28.6 percent and Sarkozy 20.7. A second round was needed because no candidate secured a majority.

All French citizens over 18 — whether they are members of the Republicans party or not — were eligible to vote in the primary, if they paid 2 euros in fees and signed a pledge stating they "share the republican values of the right and the center."