Benjamin Netanyahu is set to becomes Israel’s longest-serving Prime Minister as his 13-year rule surpasses that of Israel’s founding father David Ben-Gurion on July 20. But as he is about to cross the milestone, Mr. Netanyahu faces perhaps his greatest political challenge yet. After failing to form a parliamentary majority following the April elections, the country is holding a repeat vote in September. The following month, he faces a hearing with the Attorney General, who has recommended indicting Mr. Netanyahu on corruption charges. If formal charges are filed, Mr. Netanyahu could be forced to step aside. Mr. Netanyahu has often said he would like to be remembered as the “protector of Israel.” But admirers and critics alike say that what sets him apart is his unparalleled political acumen, a ruthless drive to win at all costs and an uncanny ability to sell his shifting policies to the public. “His marketing skills are so amazing that he can argue for one thing and then the opposite with the same conviction. It’s an art form,” said Aviv Bushinsky, a former Netanyahu aide.