PARIS—Former French president Nicolas Sarkozy denied wrongdoing on Tuesday at his trial over the illegal financing of his failed 2012 reelection campaign, saying its expenses were not his responsibility. It had never been expected of his predecessors to scrutinize campaign bills, he told the Paris court. “Can you imagine me going into a meeting to discuss the cost of flags?” he said. “I wouldn’t have lasted two minutes. I had too much to do.” The trial casts another ignominious pall over a political career that once saw Sarkozy bestride the national and global stage but later fall from grace when he was convicted in a separate case of trying to bribe a judge and peddle influence in order to obtain confidential information on a judicial inquiry. Prosecutors allege that Sarkozy’s conservative party splurged nearly double the 22.5 million euros ($27.28 million) allowed under electoral law on extravagant campaign rallies, then …