French rock star Johnny Halliday's plans to leave the country have sparked a political row.
The singer, who is a high-profile supporter of the centre-right interior minister Mr Sarkozy, is moving to Switzerland to escape French taxes.
Francois Hollande, leader of the rival Socialists, joked it was "a really nice way to support his chosen candidate".
Mr Hollande told French station Radio J: "If he really thought Nicolas Sarkozy could win, and was so convinced by his policies, he only had to wait four months."
And at a rally, left-wing candidate Segolene Royal said she had deliberately avoided "having as a friend someone who escapes to Switzerland to pay their taxes".
President Jacques Chirac, who presented Hallyday with the medal of knight in the Legion of Honour in 1997, said he valued Hallyday as a friend and an artist but regretted his actions as a citizen.
Mr Sarkozy has declined to comment directly.