After several months of 'will he,won't he', France's ex-leader announced his return to the cut-throat political front-line despite being directly or indirectly involved in several graft investigations.
The energetic 59-year-old - who inspires hate and adoration in roughly equal measure - made the announcement in a very 21st century way, via a declaration on his Facebook page.
"After a lengthy period of reflection, I have decided to offer the French people a new political choice," he said.
A political heavyweight who earned the nickname "bling-bling" for his flashy style, Sarkozy once told journalists they would never hear from him again if he lost the 2012 polls.
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But his comeback comes as his one-time nemesis Francois Hollande struggles to contain an economic crisis that has seen his popularity sink to record lows.
Experts say Sarkozy's return might have the ironic effect of boosting Hollande, as it will deflect attention from his own failures and give him someone to aim at.
"For Francois Hollande, for the government, for the left, it's definitely good news," said political scientist Eddy Fougier.
However, experts warn a Sarkozy comeback will be no easy feat.
"He had gradually forged the image of a wise man who stayed on the edge of the river and who only made comments every now and then," said Pascal Perrineau from the Institute of Political Studies in Paris.
"But if he becomes UMP president, he will be asked for his opinion on everything every morning. There is a risk he will be worn down."
Chief among these is Alain Juppe, a popular politician who served as defence and then foreign minister under Sarkozy and has announced he will stand for UMP primaries planned for 2016, with a view to running for president the following year.