Just after coming in fourth in last month's presidential election, Left Front leader Mélenchon announced he would run for the seat in Hénin-Beaumont against Front National (FN) leader Marine Le Pen, who came in third in the presidential race.
Their campaign has turned this 26,000-person town with about 20 per cent unemployment into a stage for a national standoff between the hard left and the far right.
Visiting Hénin-Beaumont's twice-weekly market is a necessary stop for any candidate running for office here. For Marine Le Pen, it's no exception.
She walks between stands that sell produce and clothing, accompanied by Steeve Briois, the party's national secretary and a local politician.
They are surrounded by four bodyguards and are accompanied by a camera crew and a handful of journalists.
In contrast to many people's reaction during the presidential campaign, people are happy to talk about their support for the FN leader, though few agree to give their last names.
"I believe her. She said she came here because the town is depressed. She's here to help and I think she's sincere," says Claudine, a 40-year resident of Hénin-Beaumont.
Neither Le Pen or Jean-Luc Mélenchon are from Hénin-Beaumont or the region. Critics call their candidacies "parachutage" - they parachute in and take the limelight.
Green party candidate Marine Tondelier, who is a local and has run in local elections since 2009, is not happy with the fact that this election has become about the two national candidates and not about local issues.
"It's quite shocking, it's like a circus. All of a sudden you have all the journalists who come like a circus, a safari. It's a bit shocking when you live here," she says.
Hénin-Beaumont has become something of a base for the FN in recent elections, as has the Nord-Pas-de-Calais region. A former mining town, it and the surrounding region were once a stronghold of the French Communist party.
The town is still run by a left-wing coalition but the FN gained traction particularly after a corruption scandal involving a Socialist former mayor in 2009. But while FN candidates have so far managed to come in first in the first rounds of parliamentary and presidential elections, they are then beaten in the second round, usually by a candidate on the left.
Le Pen came in first in Hénin-Beaumont in this year's first round of the presidential election with 35.48 per cent of the vote. But the Socialist candidate, now-President Francois Hollande, solidly won the district with 57.85 per cent.
This would suggest that the Socialist candidate for the legislative seat could fare the same. But, coming after the corruption scandal, Jean-Luc Mélenchon has changed that.
"He's a bit in the lost and found box," says Bernard, referring to the Socialist candidate, Philippe Kemel, the mayor of the nearby town of Carvin.
Bernard says he knew there was a Socialist candidate running but was not sure of his name.
"I knew [there was a candidate], but since all we talk about is Mélenchon, he ends up in the lost and found."
"The campaign has turned into a second round of the presidential election. I call it the losers' round," says Kemel as he meets the people on the market.
Wearing a suit, and accompanied by local Socialist party members handing out leaflets, he denies feeling eclipsed by the two more famous candidates. But as he shakes hands with voters, he evokes the name of the Socialist president, not his own.
"I'm the candidate with François Hollande, running for a real majority," Kemel says over and over again.
"We must give François Hollande a parliamentary majority," he tells voters, adding that he believes they will come around to voting for him.
"They know that François Hollande is president and that he must succeed, so even if they don't fully believe in him, they shouldn't block him."
A recent opinion poll shows Marine Le Pen coming in first in the first round of the election, with 34 per cent of the vote, followed by Mélenchon and then Kemel. The combination of the votes for Mélenchon and for Kemel would beat Le Pen in the second round and one of the two will drop out of the race to make that happen.
"There will not be three candidates," says Albert Facon, the incumbent Socialist MP in a neighbouring district who won against Le Pen in 2007. "There will only be two candidates. That's called republican discipline, which is always respected here."