Any US citizen that is not naturalized is constitutionally eligible to be president. That includes Rubio. This includes american babies born in foreign countries. if born to american citizens in those countries temporarily. I have a nephew born in a foreign country in a local hospital while his father was working for US naval base. He got local Birth Certificate at the hospital and then a US birth certificate a few days later from the US consulate. It was issued from the state of his parents last residence in the US. He is a us citizen from birth even though born in another country