Mr Fillon, a former prime minister who compares himself to Ronald Reagan and Margaret Thatcher, resoundingly defeated Bordeaux Mayor, Alain Juppé, in the runoff of the ''Républicains'' primary yesterday, garnering 66% of votes according to counts from 96% of polling stations.
The upset forces France's mainstream parties to rethink their approach to Marine Le Pen, an anti-immigrant euroskeptic, who polls show would easily reach the second round of next year presidential election. With the more staunchly conservative, Mr Fillon as the center right's standard bearer, the party will come under more pressure to drive turnout among right-leaning voters.
Francois Fillon's victory presents the ''Front National'' with a strategy problem. He calls for deep spending cuts, loosening labor laws that protect workers and tax breaks for business and the rich. If elected in the spring, Monsieur Fillon would slash half a million public sector jobs and $106 billion in public spending, abolish the 35 hour workweek and raise the retirement age and roll back parts of same sex couple's adoption law.
The ''Front National'' has reason to fear Fillon. His traditionalist and socially conservative line on family values and the Christian roots of France, his emphasis on French national identity, sovereignty and patriotism, his hard line on immigration and Islam as well as pro-Putin foreign agenda against ''America Imperialism'' all overlap with some of Marine Le Pen's key ideas.
This could potentially see Fillon steal some of Marine Le Pen's most socially conservative voters, particularly right wing elderly people, who always have a big turnout to vote but remain skeptical about the ''Front National''. However, Fillon might struggle to appeal to the lower middle class and working class voters who are afraid of losing their jobs.
This leaves Marine Le Pen a wide margin in which to go for Fillon's jugular as she fights a campaign centred on the people versus the elite. The Front National has already begun attacking Fillon as snobbish, political has been. It argues that Fillon, as Nicolas Sarkozy's prime minister, was responsible for the failures of the Sarkozy era and cares more about the rich, globalized elite than the working class who have faced decades of mass unemployment.
On the economy: Fillon has promised a radical shock for France with free-market reform, major cuts to public sector jobs and reducing public spending. Le Pen claims to represent the forgotten French underclass and has economic line that is essentially left wing: she is anti globalization and favors protectionism and state intervention.
On the eurozone, Fillon has backed the creation of a common eurozone treasury and the establishment of an independent ''general secretary'' divorced from the European Commission to lead on governance matters in the single currency area. Marine Le Pen has by contrast called for France to leave the eurozone and promised a series of reflationary economic measures, including reviving France's declining heartlands.
A Fillon's victory in the spring could also usher in a ''Conservatism Revolution'' via a Gallic brand of Thatcherism mixing economic liberalism with social conservatism, the likes of which France has never seen.
By Guylain Gustave Moke
International Affairs Expert