It is in the Constitution - it just requires a little reading comprehension. They clearly made a difference between a Representative, a Senator and a President.
To become a Representative -
No Person shall be a Representative who shall not have attained to the Age of twenty five Years, and been seven Years a Citizen of the United States, and who shall not, when elected, be an Inhabitant of that State in which he shall be chosen.
To become a Senator -
No person shall be a Senator who shall not have attained to the Age of thirty Years, and been nine Years a Citizen of the United States, and who shall not, when elected, be an
Inhabitant of that State for which he shall be chosen.
No person except a natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President; neither shall any Person be eligible to that Office who shall not have attained to the Age of thirty-five Years, and been fourteen Years a Resident within the United States.
Cruz has suggested that the issue was put to bed once and for all by a Harvard Law Review article published 12 days before he launched his campaign. In the article, two former top Justice Department lawyers, Paul Clement and Neal Katyal, wrote “there is no question that Senator Cruz has been a citizen from birth and is thus a ‘natural born Citizen’ within the meaning of the Constitution.â€