Ahmed Shafiq -- fallen strongman Hosni Mubarak's last premier -- endorsed Field Marshal Abdel Fattah al-Sisi, whose popularity surged afer he ousted the Islamist Mohamed Morsi last July following mass street protests against his turbulent year-long rule.
Shafiq narrowly lost the election that made Morsi Egypt's first democratically elected president, and the first civilian to take the post.
A former air force commander who was recently acquitted of corruption charges, Shafiq called Sisi the "strongest candidate who has the highest chances of winning the presidency".
Since ousting Morsi, Sisi has emerged as Egypt's most popular political figure and a nationalist icon, with supporters viewing him as a tough leader who can restore stability after three years of unrest roiling the country since the fall of Mubarak in February 2011.