Who can best reform France? That is the question French voters will answer Sunday when they elect a new president, either front-runner Nicolas Sarkozy of the ruling, center-right UMP party, or Ségolène Royal from the left-of-center Socialist Party.

For once, there is a consensus across three-quarters of the French electorate that something must be done to reinvigorate France's sluggish economy and change the way its aloof and bloated bureaucracy serves its citizens.

Because France is one of Europe's "Big Three" (along with Germany and the United Kingdom), the outcome of this election will help determine whether the United States will have a united and thriving European partnership across the Atlantic.

So what are the two candidates offering the French people, and which of them is more fit to ease social tensions and lift France out of its economic underperformance?

In some ways, what France is facing is a choice between Gallic versions of Margaret Thatcher and Tony Blair, the U.K.'s two most successful postwar prime ministers. Sarkozy, although he has been both finance and interior minister under current President Jacques Chirac, portrays himself as an outsider who will finally enact the break with the status quo that France needs.

Like Thatcher, he openly admires the American can-do spirit and its less regulated economy. He is the radical reformer on the right who says he thinks France needs more of the U.S. work ethic to succeed. But he also has gotten into trouble with the rough language he used to describe youths who rioted in protest against the hopelessness found in many of Paris' suburbs.

Royal, governor of a state in western France and a product of France's finest professional schools, is France's first female presidential candidate. She speaks a new political language, one that emphasizes reconciling French society's differences by improving the way local schools, police, day-care centers and other state agencies interact with French families.

Although she is cautious about doing away with too many of France's cherished - but expensive and probably unsustainable - welfare-state benefits, she has pushed (as Blair did with the Labor Party) for her old-fashioned Socialist Party to move toward the political middle ground.

She has hinted, for example, that as president she would offer cabinet positions to members of the new, centrist Democratic Party led by François Bayrou, the former education minister and horse farmer who came in third during the election's first round two weeks ago.

Both candidacies entail certain risks. Sarkozy has endorsed a number of protectionist trade policies, and Royal has warned about Anglo-American-style capitalism.

One could also ask why Sarkozy will be effective in reforming France's economy when two different prime ministers in 12 years of conservative rule were unsuccessful in their attempts. Another issue is whether Royal's emphasis on broad social change would provide the right kind of spark to create a more dynamic and entrepreneurial economy.

In the foreign policy domain, the bitter aftertaste left by the U.S. decision to go to war in Iraq, despite the deep skepticism of its allies, continues to affect how the French view the United States. While neither Royal nor Sarkozy is likely to antagonize the United States in the way Chirac did in the run-up to the war, they will be independent-minded and at times critical friends.

Royal shies away from the kind of open admiration of the United States that Sarkozy voices, but she has taken a tougher stance on Iran than her opponent by arguing that Tehran should have neither civil nor military nuclear capabilities.

Sarkozy, on the other hand, probably would bring French foreign policy in the Middle East more in line with U.S. policy, and he has taken a more positive approach to Israel, a close U.S. ally, than has been the case in recent years.

Whoever wins Sunday, the United States will find a France that acts more like a friend and that will be headed toward some form of economic and social reform. The crucial factors will be whether France's next president will be able to avoid gridlock at home; work with the leaders of the U.K., Germany and other key countries to improve the European Union's capacity to build a common approach to global challenges; and develop a pragmatic relationship with this and - perhaps more important - the next U.S. administration.

BY DONALD BANDLER AND PETER RASHISH

Donald Bandler, former chargé d'affaires to France, is senior director and Peter Rashish, member of the Club des Vigilants, is senior adviser for Europe at Kissinger McLarty Associates, an international strategic advisory.