Macron is trailing his predecessor by 1 percentage point, and he went on to be named France's least popular leader in recent history.
Sarkozy could face a one-year prison sentence if convicted.
A runoff is expected between Francois Fillon and Alain Juppe for the right to face the National Front's Marine Le Pen in the presidential election in 2017.
Alain Juppe is the favorite, with former president Nicolas Sarkozy and Francois Fillon also vying to face National Front leader Marine Le Pen.
Socialist incumbent president is expected to declare whether he will stand by December.
Alain Juppe and Nicolas Sarkozy are the leading contenders for the Les Republicains' nomination for president.
The ex-French president wants radicalization suspects to be expelled from the country.
The president of a leading French Muslim group said that imams must respect the laws of the country
Six former officials in Sarkozy's presidential administration have been linked to a polling scandal
The house voted in favour of reinstating fines and prison sentences for sex workers.
Francois Hollande's Socialist party set to lose half its departments as ex-president calls for change.
French security experts cite a lack of manpower for failings in the run up to this week's attacks
This week's murders at the French satirical magazine will feed extremists on all sides.
Sarkozy knows only a landslide win will deter party rivals from challenging him for the presidential ticket
The Front National leader was overwhelmingly shown to be the most popular candidate for the French presidential elections, ahead of Hollande and Sarkozy
The teenage sons of Nicolas Sarkozy and Francois Hollande's former companion Valerie Trierweiler have been involved in a four-month long Twitter feud