Any moment now the entire Olympique de Marseille team will be arrested for fraud. Or get wiped out by a meteorite. Or give up football to go cultivate pomegranates on a kibbutz. Yes, one of those things will come to pass. Unless something completely unimaginable happens ... and OM actually go and win the league.

For the past 17 years Marseille have been not so much a sleeping giant as a hapless drunken giant with recurring bullet wounds in its feet. Since 1993, when OM won the Champions League before being stripped of their domestic title and demoted for match-fixing, disgrace and disappointment have been the club's watchwords. On the brink of bankruptcy in 1996 they were rescued by Robert Louis-Dreyfus, a Franco-Swiss billionaire acclaimed in the business world for his acumen as a troubleshooter, most notably transforming the fortunes of Saatchi & Saatchi and Adidas. But at Marseille he succeeded only in depleting his own fortune and reputation.

During his 13 years in charge of OM RLD invested more than €200m (£175m at current exchange rates), hired 19 managers, copped a suspended prison sentence for making illegal payments to players, lost two French Cup finals and two Uefa Cup finals and, despite the presence of Drogba, Ribéry, Pires, Ravanelli, Nasri and Gallas, did not collect a single trophy (he remained dignified enough not to count the 2005 InterToto Cup). "Marseille has been the one failure of my life," he said shortly before dying last July and leaving the club to his wife, Margarita, reportedly with instructions not to sell it for at least 99 years.

Perhaps that is how long he thought it would take to overcome the curse that seemed to afflict the club during his reign. But instead it seems that the last manager headhunted by Louis-Dreyfus, Didier Deschamps, has broken the spell. Beating Bordeaux in the League Cup final three weeks ago gave RLD a posthumous major honour, and Deschamps seems set to restore Marseille to the French throne. Wednesday's victory over Sochaux represented more than the quashing of another bete noire – Sochaux had beaten OM on their last three visits to the Stade Bonal – it was also a mighty stride towards the title: with six games to go Marseille are five points clear at the top.

Naturally, it has not been plain sailing. At the winter break Marseille were 11 points behind the leaders Bordeaux and as far as many supporters were concerned Deschamps was exhausting the reserves of goodwill accumulated during his playing career, in particular his captaining of the club to Champions League glory. Deschamps's predecessor, Eric Gerets, had been popular before an oh-so-typical falling out with the club's hierarchy led to him accepting a lucrative offer to go manage in Saudi Arabia.

Deschamps immediately set about dismantling a squad that had seemed to be on the right track, having finished runners-up last season. He sold a slew of players, including captain Lorik Cana to Sunderland, and seemed to ostracise others who had thrived under Gerets, in particular Mathieu Valbuena, Hatem Ben Arfa and Hilton. His expensive replacements were suspect: Fernando Morientes hardly ever plays, even on his rare appearances on the pitch; Gabriel Heinze took a pay-cut to join from Real Madrid but still became Ligue 1's highest paid player and his coupling with another recruit, Souleymane Diawara, in the centre of defence quickly, and some might say predictably, turned out to be ill-advised; and the club's record signing, the €18m Argentinian midfielder Lucho Gonzalez struggled to live up to his price tag, reputation and billing.

Double D fronted up. He made adjustments, shunting Heinze to left-back and putting the midfielder Stéphane M'bia alongside Diawara in defence. M'bia says he hates the role but the change has brought a degree of solidity, both in the centre and on the left, where Heinze has proved more reliable than Taye Taiwo. But most significantly of all Lucho, free of the injuries that had hampered him earlier in the season, has confirmed what anyone who saw him during his four years at Porto knew: that he is a player of rare class. His vision and the speed and precision of his passing have conferred formidable fluidity on the team and he now has more assists than any other player in Ligue 1.

His reborn confidence and successful adaptation to Marseille was confirmed in the second half of the league game against Lyon four weeks ago, when he finally demanded to take all the team's set-pieces. Since then his corners have lead to six goals, including the winner against Sochaux. What a pity Diego Maradona seems unlikely to take him to the World Cup, apparently blaming Lucho for one of the greatest fiascos of his reign – the player's only appearance was in the 6-1 defeat in Bolivia.

That match against Lyon was significant for other reasons. Lyon had arrived in resurgent form, seemingly having digested their own early-season woes and ready to reclaim their title, while Marseille were starting to wobble again – they had drawn their previous two league games and been knocked out of the Europa League by Benfica. This, then, was to be a pivotal game in their season, precisely the sort of match Marseille have lost in previous campaigns over the past 17 years. But the greatest change that Deschamps has brought has been to Marseille's mentality. This serial winner has taught Marseille to use pressure as a fuel rather than a drain and in a high-octane game they scored late to beat Lyon 2-1. The following weekend they bullied Bordeaux into submission in the League Cup final and they've won every game since.

Part of the reason for Marseille's rise – and part of the reason why they look unlikely to fall – has been the demise of Bordeaux. Wednesday's defeat by Le Mans was the third league loss in a row for Laurent Blanc's team, whose relatively small squad appears jaded by the attempt to challenge for trophies on three fronts. Tomorrow they face Lyon in a match where the result could definitively end the title aspirations of at least one of Marseille's big rivals.

That Auxerre are currently second in the table shows that disparities of wealth in French football have not yet become as pronounced as in England, so a well run club can still challenge for the title against rivals with much greater resources. Jean Fernández's side are a sort of French Fulham, a compact unit who, unlike last season when they were deathly boring, have learned to penetrate as well as smother. Against the top teams they have counter-attacked with particular success, and have taken 16 points from a possible 21 from their matches against the top six. In three weeks' time they host Marseille. They are the biggest obstacle on OM's road to the title, except perhaps, even now, Marseille themselves.