Former French prime minister François Fillon, a member of the Republicans political party, on Sunday won the country’s first-ever conservative presidential primary. (Christian Hartmann/Reuters)

François Fillon on Sunday won France’s first-ever conservative presidential primary after promising drastic free-market reforms and a crackdown on immigration and Islamist extremism. Fillon defeated a more moderate rival who had warned of encroaching populism.

“President! President!” chanted the former prime minister’s supporters as he declared victory over Alain Juppé in a nationwide runoff election.

Polls suggest that the 62-year-old Fillon, prime minister from 2007 to 2012 under President Nicolas Sarkozy, has a good chance of winning the presidency in the April-May election.

Fillon campaigned on promises of slashing public spending, capping immigration, supporting traditional family values and forging friendlier ties with Russian President Vladimir Putin. Fillon enjoyed a surprise surge in popularity in recent weeks over longtime front-runner Juppé, who also previously served asprime minister.

In a sober victory speech, Fillon promised to defend “French values” and said France needs “a complete change of software.”

Fillon, whom Juppé had accused of running a divisive campaign that catered to the far right, struck a slightly more inclusive tone on Sunday night.

“No one should feel excluded from a society that I want to see more just and with more solidarity,” he said.

During the primary campaign, Juppé, 71, expressed similar ideas as his rival on the economy but tried to rally conservatives around a more tolerant attitude toward France’s ethnic, religious and social diversity.

With results being reported from 96 percent of voting stations, organizers of the Republicans party primary said Fillon had 66.5 percent of votes compared with Juppé’s 33.5 percent.

Fillon’s toughest challenge ahead is likely to be far-right leader Marine Le Pen. Le Pen is running an anti-establishment campaign that particularly targets immigrants, France’s large Muslim minority and the European Union.

Socialist President François Hollande is expected to announce in the coming weeks whether he will seek reelection. The French left has been deeply weakened by Hollande’s extreme unpopularity.

Both Fillon and Juppé are high-profile leaders of the Republicans who knocked their former boss —Sarkozy — out of the primary’s first round of voting a week ago. Sarkozy then threw his weight behind Fillon.

Sunday’s runoff came after a bruising end 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 wants to drop sanctions against Russia over its aggressive actions in Ukraine and partner with Russia in the fight against Islamic State extremists. He insists “Russia poses no threat” to the West.