When Nicolas Sarkozy held his first comeback rally, he sweated profusely on a small stage in a stuffy and spartan gymnasium in the south of France.

The rightwinger’s modest choice of venue last month to launch his campaign to become his party’s 2017 presidential nominee contrasted strikingly with the glitzy, US-style stadium gigs that became a trademark of the man once known as President Bling Bling.

In 2012, when Sarkozy ran for re-election and lost to the Socialist François Hollande, his rallies were theatrical mega-productions, slickly coordinated by dedicated film directors, with specially laid carpet for his luxury dressing rooms and tens of thousands of euros spent on French flags to be waved by a sea of adoring fans.

Those mega-rallies came back to haunt him this week when the French state prosecutor recommended Sarkozy should face a criminal trial over alleged illegal campaign funding.

The case centres on an alleged system of false accounting used by Sarkozy’s office to conceal an enormous campaign overspend – namely on lavish rallies – in 2012. The limit on presidential campaign spending in France is €22.5m (£19m), and investigators suspect Sarkozy’s campaign spent €23m on top of that. Sarkozy has always denied any wrongdoing in the case, or even any knowledge of Bygmalion, an events company that allegedly concealed the overspend.

The prosecutor’s recommendation that Sarkozy face trial is a serious knock to his attempt to win back power next year on a platform of hardline identity politics and a security crackdown. The man presenting himself as a model of “French authority” is suddenly facing the possibility of standing in the dock.

But Sarkozy is defiant. He has hit back with the same argument he has used about a string of legal investigations that have dogged him since 2012: that he is innocent of any wrongdoing and that he is the victim of a plot against him by political enemies in cahoots with the justice system.

“No controversy, no manoeuvring, no manipulation – however shameful it may be – will deter me from my absolute determination to bring about a change in power,” Sarkozy told a rally west of Paris on Tuesday night. “I love France!” he thundered. “Trying to discourage me from my passion is inhuman – it’s not possible!” The crowd cheered and applauded. “I like people who have their ups and downs, who don’t complain, who grit their teeth,” he told supporters.

Sarkozy’s strategy of presenting himself as a victim is likely to comfort his unfailing support base inside his own Les Républicains party. The news that the state prosecutor wanted Sarkozy to stand trial came on the same day as a major fraud trial opened against Hollande’s onetime senior lieutenant and budget minister Jérôme Cahuzac, who is accused of tax evasion and money-laundering – raising eyebrows on the right about the timing of the announcement.

A Sarkozy election rally in 2012. Photograph: Eric Feferberg/AFP/Getty Images

But outside this devoted, narrow support base, Sarkozy’s legal woes could prove a slow poison that permeates the right’s primary campaign. Voters on the broader right and centre who will nominate their presidential candidate in November might decide that the spectre of a court case is too damaging to Sarkozy’s chances of winning back the presidency. Fabrice Arfi, the investigative journalist for Mediapart, described Sarkozy’s claims he was being victimised by the justice system as a “Berlusconian gesture”. It will be difficult to have to keep answering questions on this during the primary race TV debates.

And yet, as has often been shown, legal investigations are not necessarily a mortal blow in French politics. Other political figures have happily skipped up the French ladder of power unburdened by hefty legal baggage that might have pulled them down in other countries – not least the former president Jacques Chirac.

Nothing prevents Sarkozy from continuing to run to be his party’s presidential candidate. He is innocent until proven guilty. It is now up to an investigating magistrate to decide whether to put Sarkozy on trial. This decision may or may not come before the right’s primary vote. Any trial is unlikely to happen before the presidential race next spring. In any case, if Sarkozy were to be chosen as the right’s candidate, then ran for president and won, he would have presidential immunity.

Sarkozy supporters wave flags at 2012 campaign event. Photograph: Pascal Parrot/Reuters

Sarkozy’s name has been cited in such a bewildering array of legal investigations – from allegations of illicit campaign funding from the late Libyan leader Muammar Gaddafi to alleged kickbacks from arms sales to Pakistan used to fund an earlier campaign – that voters have almost lost count. Sarkozy is under investigation for corruption and influence-peddling in a case based on phone-taps about an alleged bid by him to get information from a judge ahead of a legal decision. Sarkozy denies any wrongdoing in all the cases. Some other key investigations against him have been dropped, including allegations he accepted campaign donations from the L’Oréal shampoo heiress Liliane Bettencourt when she was too frail to know what she was doing.

It’s not clear how much political capital will be made out of Sarkozy’s legal difficulties by his opponents. Alain Juppé, the former prime minister and mayor of Bordeaux, who remains favourite to win the right’s nomination, has vowed to avoid the issue and “refrain from making personal attacks”. For good reason. In 2004, he himself received a 14-month suspended sentence and was barred from holding elected office for a year over a corrupt 1980s scheme that illegally put workers for Chirac’s political party on the payroll of Paris’s town hall. The conviction, however, has not damaged him. It is accepted that he did not profit personally and instead he is seen as having selflessly taken the flak for Chirac.

But another opponent, Sarkozy’s former prime minister, François Fillon, shows no sign of letting up. Even before the state prosecutor’s recommendation, he warned in a scathing speech: “Those who don’t respect the laws of the Republic should not be allowed to run. There’s no point in talking about authority when one is not beyond reproach. Who can imagine for a moment General de Gaulle being under criminal investigation?”