The 20 days that Nicolas Sarkozy recently spent behind bars have been turned into a book published today. The 70-year-old former president of France was convicted of criminal conspiracy after a long-running investigation into charges his aides approached Libyan leader Muammar Gaddafi for campaign funds. ‘Sarko’ was jailed for five years but he was released after 20 days while his appeal is heard.

Diary of a prisoner is Sarkozy’s account of his incarceration, written in his cell where ‘grey dominated everything, devoured everything’. But it is what the former president has written about the future of France that has made the headlines.

Sarkozy, a centre-right Republican, describes a telephone conversation with Marine Le Pen, the leader of the National Rally, whose party has the most seats in parliament. Power remains elusive for Le Pen, however, because of what the French call the ‘Republican Front’: when the other parties – the left, the centre and the centre-right – gang up against her in the second round of voting.

Over the telephone, Le Pen asked Sarkozy if he ‘will join forces with any kind of Republican Front in future elections?’ No, replied Sarkozy, ‘and what’s more, I will take responsibility for this by taking a public position on the subject when the time comes.’

Justifying his decision, Sarkozy wrote that ‘the path to rebuilding the right can only be achieved through the broadest possible spirit of unity, without exclusion or condemnation.’

Roland Cayrol, one of France’s leading political scientists, described Sarkozy’s admission as ‘a bombshell’ because ‘this is the first time that someone with such influence in a party has promoted the idea of an electoral alliance with the National Rally.’

Sarkozy still has a large and loyal fanbase, the majority of whom are urban and elderly bourgeois, a demographic that Marine Le Pen’s party has struggled to attract.

Some regard her as too left-wing on the economy and others baulk at voting for a Le Pen because of the anti-Semitic rabble-rousing of her father, Jean-Marie. That is why Sarkozy’s endorsement counts; if he backs Le Pen then so will they.

Sarkozy’s predecessor as president, Jacques Chirac, also a centre-right Republican, regarded the National Rally as pariahs. When Jean-Marie Le Pen reached the second round of the presidential election in 2002, Chirac refused to meet him in the traditional televised debate, saying that ‘faced with intolerance and hatred, no debate is possible.’

Sarkozy recognises that Marine Le Pen is not her father, as do other senior figures within the Republican party. Their leader, Bruno Retailleau, until recently the Minister of the Interior, has said that ‘National Rally belongs to the republican arc, which La France Insoumise [LFI] does not.’

LFI is the far-left party led by Jean-Luc Mélenchon, whose rhetoric frightens most of France’s Jews. Recently, a parliamentary committee investigated if there are links between the LFI and Islamist organisations.

This is one reason why Sarkozy and Retailleau have abandoned the Republican Front. In their view it is no longer the Le Pens who threaten French values but the party of Jean-Luc Mélenchon.

Another reason is the belief that the left are waging lawfare against the right in a desperate attempt to keep them from power. Sarkozy is the third major figure from the right to be found guilty of financial wrongdoing in a decade. First it was Francois Fillon in 2017 and then Marine Le Pen earlier this year.

Perhaps right-wing politicians are more dishonest than the left, or maybe there is something in the claim that the French blob, which is dominated by the centre-left, is determined to cling to the power it has held since the 1980s.

Last week the left-wing newspaper Le Canard Enchaîné – the same one that targeted Fillon – ran a story alleging misuse of funds by Jordan Bardella. According to the report, money from the European parliament allocated for media training was instead put towards the National Rally’s 2022 election campaign. As a result of the story, a left-wing organisation has filed a complaint with the National Financial Prosecutor’s Office.

Bardella, who yesterday lunched with Nigel Farage in London, has denied any malpractice and said that the ‘French are not fooled by these operations, which come just a few days after favourable opinion polls.’

That opinion poll had Bardella as the runaway favourite to win the presidential election in 2027. Another poll at the weekend confirmed that Bardella and Le Pen have a ‘spectacular’ lead over their rivals. This gap will likely grow after Sarkozy’s endorsement of the National Rally.

It feels increasingly inevitable that Bardella or Le Pen will be the next president of France unless, that is, the lawfare wins against them.