Thursday's protest brought the troubles of France's industrial heartland to Paris' elegant boulevards and the lawns beneath the Eiffel Tower.
High unemployment and France's stagnant economy are central to the campaign for elections in April and May. Many voters see the conservative Sarkozy as too friendly with the rich, and his Socialist challenger Francois Hollande is the frontrunner in polls.
About 200 workers from an ArcelorMittal steel plant in Florange in northeast France came to Paris in buses as part of a protest movement that started last month to try to save jobs at the factory. After disembarking, they tried to walk toward Sarkozy's campaign office, shouting "Thank you, Sarko!" The workers blame Sarkozy's conservative government for not doing enough to save the plant, which workers fear is going to be shut down.
They were met by riot police and gendarmes who tried to push the protesters back with shields. After several minutes of fighting, the police fired tear gas to break up the crowd.
When tensions subsided, the protesters walked toward the Eiffel Tower and tried to unfurl a huge banner from the first floor balcony, but were blocked by police.
Instead, they unfurled it on a fence beneath one of the pillars of the iconic monument, reading "Yes to Steel from Lorraine," referring to the region where the Florange plant is located. They sat peacefully on benches, chanting anti-Sarkozy slogans.
Sarkozy accused unions of overplaying the dispute and pledged to help the workers. The president had left his campaign headquarters soon before the protesters arrived. He had scheduled a meeting with the ArcelorMittal workers for next Monday, but wasn't expecting them Thursday.
"If they want an appointment, I'm ready to give it to them, but it's best if I'm here. But I will meet them because the future of the steel industry is absolutely crucial," he told reporters before leaving.
Sarkozy has taken up the workers' concerns and said that he has obtained promises of €17 million ($22 million) in investments for the Florange plant, including money to restart blast furnaces that have been dormant in recent months.
The company says the furnaces were shut down temporarily because of a global slump in demand that has also hit other ArcelorMittal plants around Europe. But unions fear that the shutdown is a step toward permanent layoffs.
Workers said police used unnecessary force in Thursday's skirmishes.
"We are not troublemakers. But they treated us as troublemakers. We just came to defend our jobs. And here's what they do to us. Look at us, at what they did to us," said Antoine Terrak, an ArcelorMittal worker, referring to the tear gas.
Sarkozy "wants to present himself as a candidate of dialogue, talks, open-mindedness, and here today, as you've seen, everything is closed to us. All the doors are closed to us. The doors of his headquarters, the doors of the Eiffel Tower," protest leader Edouard Martin said.
Socialist candidate Hollande seized on the protest to dig at the conservative government. "It's not with tear gas that the outgoing candidate will suppress their anger," he said in a statement.