While one may wonder whether President Macron will be able to withstand the heat unleashed by his decision to steamroll an unpopular pension reform bill through the French parliament, there is little question his old foe, Marine Le Pen, wants to boot him from the kitchen. 

The fate of a deeply unpopular reform bill under which the French retirement age will rise to 64 from 62 has been looming for months because Mr. Macron lacked the parliamentary majority needed to pass it by a vote. So on Thursday the French president chose to bypass the risk of a humiliating defeat for his government and opted to activate the so-called 49.3 rule, which is synonymous with forced passage of a bill. 

That did not transpire without the most raucous session of the lower house of parliament, the National Assembly, in recent memory, with opposition lawmakers variously breaking into la Marseillaise, the French national anthem, and generally raising hell to prevent the harried prime minister, Élisabeth Borne, from speaking. Ms. Borne later told French media that she was shocked by the scene.

Yet the real blow was delivered by Ms. Le Pen, who called on the prime minister to resign. She will not — at least, not right away — but the confidence with which Ms. Le Pen delivered her demand speaks to the newfound fragility of Mr. Macron’s administration. She prefaced her ultimatum by declaring Ms. Borne to be in the minority and by blasting her hewing to Mr. Macron’s line against so much opposition as “a provocation.”

This was all really a lateral punch to Monsieur Macron, against whom Ms. Le Pen, the most public face of the National Rally, ran for president twice. She lost both times, but in last year’s rematch Mr. Macron’s victory was less robust. 

Marine Le Pen is one of the savviest politicians in the business and knows how to play the long game. She is also demonstrably a better judge of the French national mood than Mr. Macron, and right now that mood is one of outrage. Upon learning of the activation of the 49.3 rule, spontaneous demonstrations erupted across France. Scuffles with riot police were seen at the Place de la Concorde at Paris and were reported in major regional cities such as Dijon and Rennes. 

The head of the CFDT trade union, Laurent Berger, tweeted, “By resorting to 49.3 the government is demonstrating that it does not have a majority to approve the two-year postponement of the legal retirement age.” Mr. Berger called for more strikes, which are expected to ripple across multiple sectors of the French economy as soon as next week. But scenes of the French social fabric coming apart at the seams were already beamed across European television screens; this week may actually be the calm before the storm.

That is because next week is pivotal for another reason beyond the general inconvenience of public sector strikes and work stoppages: the opposition, chief among them Ms. Le Pen, is gearing up for a vote of no-confidence in the Macron government. The process starts next Wednesday when the Commission Mixte Paritaire meets in the senate to discuss the text of the bill. 

The commission consists of seven deputies and seven senators. They will attempt to find a compromise ahead of final reading of the bill that must occur in the National Assembly by March 26. However, it is unlikely that the two opposing camps will agree on much, if anything. Since 1958, one-third of CMP meetings have resulted in the failure to reach an accord. 

If that should happen and the activation of provision 49.3 proceeds, a censure motion to topple the government will swiftly follow, with Ms. Le Pen leading the charge. 

In the overheated social climate prevailing in France right now, just how long Monsieur Macron can hang on after that is anyone’s guess. He might have already given a hint, though, when he said that he decided to override a normal parliamentary vote to ram his reform package though because “the financial and economic risks are too great” to do otherwise. 

That was seen by some French  pundits as a veiled allusion to what happened in Britain after the presentation of the “mini-budget” by a former prime minister, Liz Truss, and her chancellor of the exchequer, Kwasi Kwarteng. After their announcement of tax cuts with nebulous financing, interest rates soared, leading to an intervention by the central bank of England to calm the storm. Ms. Truss ended up resigning a few weeks after the humiliating episode, making her term as prime minister the shortest in British history.

Mr. Macron is now well into his second term, so the situations are not totally analogous. Yet Ms. Le Pen is a strong woman who knows not only how to strike, but when.