PARIS — France is set for a battle for the presidency between a conservative and a liberal after exit polls from the first round of voting yesterday indicated that Nicolas Sarkozy and Segolene Royal had cruised into the second round.

The head of the ruling conservative Union for a Popular Movement party, Mr. Sarkozy, scored 30%. About 11 million voters backed the charismatic former interior minister.

The socialist candidate, Ms. Royal, came in second, with about 26%. The pair will now fight it out on May 6 in the battle to succeed the president, Jacques Chirac.

Early results showed that the two other top contenders, the leader of the centrist Union for French Democracy, Francois Bayrou, and the far-right leader, Jean-Marie Le Pen, were no longer in contention.

Mr. Bayrou looked set to come in third, with 18%, leaving Mr. Le Pen trailing at about 11% — lower than the 16.8% he scored in 2002 and his worst score in four elections.

The result heralds the promise of a showdown between an uninhibited right, offering liberal reforms and an emphasis on work and meritocracy, and a left offering a change in leadership style while seeking to preserve a generous welfare system.

The victors must now try to reach beyond their electoral bases. The main challenge is to win centrist voters who chose in favor of Mr. Bayrou.

“The question mark hanging over Royal is competence. The question mark hanging over Sarkozy is character,” the editor of L’Express magazine, Christophe Barbier, said.

Mr. Sarkozy created the first surprise of the day by voting alongside his wife, Cecilia Sarkozy. There had been recent rumors that the pair had separated and Mrs. Cecilia, a key adviser, had not been seen in campaign headquarters for weeks.

Mr. Sarkozy, 52, has sought to poach traditional voters for the National Front leader, Mr. Le Pen. Many more may now turn to him now that the Mr. Le Pen is out of the race.

Voters from the left and the center may band together against Mr. Sarkozy in protest of his authoritarian style, his pro-Americanism, and his relatively liberal economic policies.

Mr. Sarkozy is despised by immigrant residents of the suburban housing estates, who accuse him of stoking the 2005 riots by calling delinquents “scum.”

His detractors cite his pledge to create a ministry of immigration and national identity as proof of anti-immigrant tendencies. His recent remark that there may be a genetic explanation for pedophilia and teenage suicide is held up as proof of his eugenic beliefs.

“We have today a political situation I have never seen: a man who is highly likely to be the next president but who provokes unprecedented levels of hatred and rejection,” a professor at the Paris School of Political Sciences, Dominique Reynie, said. “To counter this, he will have to provide concrete evidence of his softer side.”

His rival, Ms. Royal, 53, faces an even tougher struggle. The left-wing electorate is estimated at around 40%, its lowest level since 1969. Ms. Royal needs to convince centrist and even National Front voters that she will honor her pledge to remain “free” from the clutches of the old-style socialism.

She has done this at times by pledging to create a socially just France with a tough moral backbone, including a plan to create “boot camps” for young delinquents.

Rather than targeting big business, moderate voters will expect her to speak out for fiscal responsibility and private enterprise.

The question remains whether Mr. Bayrou will endorse Ms. Royal and create a pact to keep Mr. Sarkozy from the Elysee palace.

The idea of a Royal-Bayrou pact was broached by the former socialist prime minister, Michel Rocard, last week but quickly quashed by Ms. Royal, who wanted to maximize her first-round vote. She may reconsider in coming days, perhaps offering Mr. Bayrou and his UDF colleagues posts in a future government.

The other unknown is Mr. Le Pen, who has wavered about Mr. Sarkozy in recent weeks.

A Le Pen specialist, Romain Rossi, said it was unlikely he would formally back Mr. Sarkozy. If Mr. Sarkozy is in difficulty, Mr. Le Pen may be tempted to apply the “kiss of death” — to offer his support, which Mr. Sarkozy would have to refuse, allowing Mr. Le Pen to call on his supporters to vote against him.