In a surprise attack on the French presidential election race, the extreme leftist independent candidate Jean-Luc Mélenchon has closed the gap on his rivals, according to the latest polls. Marie Le Pen, Emmanuel Macron and Melenchon all have a chance of reaching the runoff, and as many as a third of voters remain undecided.

Melenchon, enjoying a late poll surge, campaigned on a barge Monday floating through the canals of Paris. Le Pen's nationalist rhetoric and Melenchon's anti-globalization campaign have resonated with French voters sick of the status quo. Macron also paints himself as an anti-establishment figure — seeking to bury the traditional left-right spectrum that has governed France for decades.

Far-right presidential candidate Marine Le Pen hammered on themes that pump up supporters, like immigration and national identity, at her Paris rally on Monday as France's unpredictable presidential campaign neared its finish with a grab-bag of potential outcomes.

Questions rather than clarity defined France's presidential race a week before the first-round vote to narrow the field of 11 to a May 7 runoff between the top two vote getters.

Le Pen has been jostling with independent centrist Macron for the lead in polls, while hard-left rival Jean-Luc Melenchon and conservative Francois Fillon begin to close the gap.

Scuffles between scores of opponents of Le Pen's anti-immigration National Front party and riot police broke out ahead of her rally, delaying its start. Her campaign director announced to the crowd of thousands that a party lawmaker had been attacked on his way in, denouncing the masked youth as "extreme-left scum." Lawmaker Gilbert Collard was unharmed. A woman later jumped onto the stage as Le Pen spoke but was quickly slammed to the floor and removed.

In her speech, Le Pen, who says France has been subjugated by the European Union and waves of mostly Muslim immigration, called the upcoming vote "historical." "What is being played next Sunday is an issue of civilization."

The race is being watched internationally as an important gauge of populist sentiment, captured notably by Le Pen, with her nationalist program presented under the slogan "In the Name of the People."

Le Pen vowed Monday to end the borderless Schengen Treaty so France can control its frontiers and with that, she claims, stop both immigration and the terrorist threat.

"We opened the door of the house of France to the mafia, to terrorists who quickly understood the benefits they could get from our incredible powerlessness and send their soldiers of hate among the migrant flows to hit our country in the heart," she said. The crowd stood, cheered and chanted, "On est chez nous," or "We are in our land."

Macron, the former economy minister in the Socialist government and one-time investment banker, promised an "open, confident, winning France," painting that as a contrast to his far-right and far-left rivals and their anti-system platforms.