In Paris, the municipal election campaign has well and truly begun. If anyone still doubted it, they just had to note the reactions to the Observer’s article last weekend on the dirtiness of the French capital. Under a headline condemning Paris as “the dirty man of Europe”, Kim Willsher wrote how, despite the efforts of the city’s authorities to improve the cleanliness of streets, this is an issue that is causing considerable concern to Parisians. She quoted an American professor who has lived in the city for the best part of 30 years as saying that Paris was “filthy everywhere”. And even if the piece reminded us of the large amount city hall spends on cleaning the city – around €500m (£445m) a year – and noted its “grand schemes” to combat air pollution, it certainly touched a nerve.

Paris was no worse than any other major city, insisted some angry readers on social media. Le Parisien described it as a “vitriolic article”. The mayor, Anne Hidalgo, had to go on French radio to defend her record and said the same sort of article had been written about Rome and London. She couldn’t put a rubbish collector behind every Parisian, she declared.

Hidalgo’s opponents seized on her response as fresh evidence of a lack of willingness to tackle the subject, while her supporters saw the whole thing as an all-out attack.

Why such a response? Willsher has noted that articles by Spanish or Italian journalists recently published on the same subject have not aroused such virulent reactions.

In my opinion, the explanation is to be found in the very special relationship between France and England. Enemies for hundreds of years, our two countries have managed to mitigate their ancestral rivalry with time and, during the second world war, responded to the call of history, sealing their alliance with the spilling of blood.

Still, in the collective unconscious – on both sides of the Channel – a certain sensitivity persists.

But what of the substance of Willsher’s piece? It is hard to argue with that. Even Le Parisien, asking “Is Paris really that dirty?”, ran a video last week showing city streets with litter and dog dirt as well as overflowing rubbish bins. The magazine where I work, Marianne, ran a piece in March under the headline: “Behind the postcard, Paris dustbin city”. Beyond a few quibbles from city hall staff on the choice of our cover photo, the matter rested there.

Since then, a new element has entered the equation: the appearance of new candidates challenging Hidalgo in next year’s elections, including a former government spokesman, Benjamin Griveaux, and the mathematician Cédric Villani, also an MP.

A fun detail is that they are both supporters of Emmanuel Macron. Winning over Paris represents a major challenge for the republic’s president. If Macron’s friends take the capital in 2020, it would allow him to enter a second presidential election under the best auspices.

The opposite result would be perceived as a dark omen. Hidalgo knows this perfectly well and is an obstacle even if, according to the latest opinion polls, she continues to lead in the municipal race by a slim margin: voting intentions put her at 24%, ahead of Griveaux at 19% and Villani on 15%.

As Willsher noted, the question of Paris’s cleanliness remains the primary concern of those who live there. The subject is sensitive. Appetites are whetted, knives are sharpened. Last week’s Observer report was only the pretext for an initial round in this municipal campaign. A first controversy to warm up. It will certainly not be the last.

Bruno Rieth is a reporter for Marianne magazine