By Nicholas Vinocur
NANTERRE France (Reuters) - Former French President Nicolas Sarkozy was held for questioning for 15 hours on Tuesday over suspicions he used his influence to secure leaked details of an inquiry into alleged irregularities in his 2007 election campaign.
It was the first time a former French head of state has been held in police custody and is the latest blow to Sarkozy's hopes of a comeback after his 2012 election defeat by Socialist rival Francois Hollande. The conservative politician denies all wrongdoing in a string of investigations involving him.
Sarkozy arrived early on Tuesday to be quizzed by police investigators at their offices in Nanterre, west of Paris. He spent all day and evening in police custody but at about 11:40 p.m. local time (1040 BST), he was seen by a Reuters journalist arriving at a civil court in Paris, where he was to be presented to judges.
Under the French legal system, being sent before the court would be the next step in the possible opening of a formal investigation against a suspect - a step that often, but not always, leads to trial.
A few hours earlier, Sarkozy's attorney and a judge involved in the case were put under formal investigation on suspicion of influence peddling, their attorneys said.
Placing a suspect under formal investigation means there exists "serious or consistent evidence" pointing to probable implication of a suspect in a crime. Investigating magistrates, rather than the police, then conduct their own probe.
Influence-peddling can be punished by up to five years in prison and a fine of 500,000 euros (£398,836). Sarkozy lost presidential immunity from legal prosecution a month after he left office in June 2012.
Allies rushed to support Sarkozy.
"Never has any former president been the victim of such treatment, such an outburst of hatred," Christian Estrosi, the mayor of the southern city of Nice and a close Sarkozy ally, said on his Twitter account.
Government spokesman Stephane Le Foll, however, said Sarkozy was "subject to justice like everyone else" and told i