Francois Fillon has won France's Republican presidential primary, after his opponent Alain Juppe conceded defeat.
Mr Fillon had won 67% of votes and Mr Juppe was on 33%, according to results from about 90% of polling stations.
The pair, both former prime ministers, were vying to become the centre-right Les Republicains party candidate in the election.
Speaking after his victory, Mr Fillon, 62, said: "I must now convince the whole country our project is the only one that can lift us up.
"My approach has been understood: France can't bear its decline.
"It wants truth and it wants action.
"I will take up an unusual challenge for France - tell the truth and completely change its software."
In Paris, 71-year-old Mr Juppe congratulated Mr Fillon on the "large victory", adding: "I finish this campaign as I began it - as a free man who did not compromise what he is or what he thinks".
He called for unity and calm after a campaign during which he had accused Mr Fillon of pandering to anti-immigrant and anti-Muslim feeling.
Mr Fillon is now likely to face a spring showdown with far-right National Front leader Marine Le Pen, who will be seeking to build on that same anti-immigrant, anti-Muslim and anti-establishment feeling.
Ms Le Pen has also promised to lower the retirement age and guarantee France's welfare safety net.
A Harris Interactive poll published on Sunday night showed Mr Fillon would beat Ms Le Pen by 67% to 33%.The victory for Mr Fillon, who is married to a Welsh woman, comes against a national unemployment rate of 10%, weak economic growth, worries about immigration and globalisation and concern about the future of a costly but valued welfare state.
In response, Mr Fillon has proposed spending cuts, increasing sales tax, scrapping a tax on the wealthy, fewer restrictions on the working week and raising the retirement age to 65.
He also wants to limit the adoption rights of gay couples, push for closer ties with Russia and focus on tackling Islamic extremism and reducing immigration to France "to a minimum".
Mr Juppe had promoted a more liberal stance with respect for religious freedom and ethnic diversity, attacking the "brutality" of his rival's manifesto.