Mr. Chirac, he added, fell not to “weaponization of the legal system,” but to shifting ethical standards. After serving as president of France, Mr. Chirac was convicted of creating fake jobs for political allies when he was mayor of Paris decades earlier.

“Some of the things that Chirac did had been common practice at the time,” Mr. Vaïsse said.

To ensure fairness — or the appearance of fairness — prosecutors, like judges, should be “insulated from political pressures,” Mr. Bellinger said, adding that “as best as possible,” they themselves should be apolitical.

He acknowledged that it was hard for officials to convince the public of their impartiality when they face constant accusations of bias and when they are appointed by elected officeholders or are, themselves, elected.

But those challenges, as difficult as they are, cannot dissuade the justice system from taking on legitimate cases against political leaders, he and other experts said.

“People will throw potshots at the process any time they’re arrested; that is common,” Mr. Levitsky said. “But if you rob a bank and I arrest you, and you threaten to throw a hand grenade at the courthouse, the problem is not that I arrested you for robbing a bank.”