Suddenly, the forces of anti-globalization are throwing France's presidential campaign into turmoil.

For a second time since the arrest of Dominique Strauss-Kahn in New York on sexual-assault charges, a presidential front-runner is staggering against the ropes, primed for a possible knock-out.

The elections, to be held in April, are particularly critical given the key role the next president will have in navigating Europe through its sovereign debt crisis.

On Sunday, the Socialist party held its first-ever American-style primary. The primary was an attempt to modernize France's democracy by giving the electorate the opportunity to decide who should run in the 2012 elections. In the past, the party elite selected the candidate themselves. Many in France welcomed the change, even if it appeared to be an oddity imported from across the Atlantic.

The polls were widely viewed as a success, attracting more than 2 million voters, each of whom was required to pay at least one euro and pledge that they adhere to the party’s values.

The results, however, are likely to be leaving operatives scratching their heads about whether letting the people decide was such a good idea.

As predicted, Francois Hollande took the largest share, at about 39 percent, followed by Martine Aubry at 30 percent. Since neither candidate won a majority, a runoff will be held between them next Sunday.

The intrigue emerges from the strong showing of Arnaud Montebourg, who placed third, giving him extraordinary influence over who gets the nomination.

Many in France's political establishment (and in the Socialist Party) had dismissed Montebourg as a left-wing firebrand who lacked gravitas. The 48-year-old deputy to the National Assembly has called for greater state ownership of banks, and has promised to save the French from the “ravages” of globalization. So radical are his ideas that he has earnestly called for rewriting the French constitution; for a decade, he has led an organization advocating this. A month ago, polls gave him 5 percent of the vote.

At a rally last night, Montebourg arrived with a rose in his hand. His supporters knowingly chanted “We won! We won!”

Montebourg's position as potential king-maker stems from winning 17 percent of the vote. This means that he claimed more than half of the votes that went to politicians other than Hollande or Aubry. Having been knocked out, he is expected to call for his supporters to back the candidate of his choice in next weekend’s runoff.

Montebourg is savoring his moment of power. He has not yet indicated who he will support. His views are clearly more in line with those of Martine Aubry than that of the more centrist front-runner, Hollande. Aubry, the architect of France's 35-hour work week, advocates government-funded economic stimulus for France. That puts her at odds with the European movement toward fiscal austerity, an approach strongly supported by Germany's Chancellor Angela Merkel.

Even if Hollande pulls off a victory, Montebourg’s strong showing is bad news for him. The Socialists, France’s second-biggest party, have not won the presidency in more than two decades. As such, the party has strived to present a united front in support of its ultimate goal: defeating the highly-unpopular incumbent President Nicolas Sarkozy. That may not be an easy task, especially if the Socialists’ newly-revealed far-left tendency alienates voters.

Incidentally, in another particularly French quirk, Hollande will also be seeking votes from supporters of Segolene Royal, who won 7 percent in Sunday’s primary. Royal, who lost the presidency to Sarkozy in 2007, is Hollande’s former domestic partner, with whom he has four children. In an additional twist, Montebourg was Royal’s presidential campaign spokesman in 2007, before he was fired for criticizing Hollande on national TV. (Royal and Hollande were still together at the time).

With six days left before the run-off, the Socialist party’s primary has turned into a cliff-hanger. Given the newfound influence that the forces of anti-globalization will have on the election, and the role that the next French president will almost certainly play in bailing out banks, rescuing insolvent countries and breathing new life into Europe’s economies, the stakes could hardly be higher.

