Francois Fillon heads into a runoff campaign for France's conservative presidential ticket on Monday, November 21 as favorite after winning the endorsement of ex-president Nicolas Sarkozy whom he ousted from the race after a stunning late surge in polls, Reuters reports.

Fillon is up against another former prime minister, Alain Juppe, who has a week to turn around his momentum-sapped campaign and win over the supporters of the other candidates.

But with Fillon only six points short of the 50 percent threshold needed in the first round and Sarkozy on his side, it looks a tall order for Juppe.

At stake is an almost certain place in the second round of next spring's presidential election, pollsters say, with the French left in turmoil under the deeply unpopular President Francois Hollande. There the conservative challenger would in all likelihood face the leader of the resurgent far-right National Front party, Marine Le Pen.

"I believe more than ever that the people of France need to come together to turn the page of a disastrous five-year term that has demeaned our country and to block from power the National Front which would lead us into the worst of adventures," a downcast-looking Juppe told his supporters.

A snap poll by Opinionway showed Fillon winning next Sunday's head-to-head contest with 56 percent of support.

Fillon and Juppe have clashed most forcefully over Fillon's proposals to slash the cost of government, most notably by axing 500,000 public sector jobs over five years.

Behind his still-boyish looks and refined demeanor, the 62-year-old Fillon is as close to a true economic and social conservative as they come in France.