Article II, Section 1, Clause 5:

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.

The Framers appear to have adopted the requirement that citizens be natural born citizens to ensure that the President’s loyalties would lie strictly with the United States.

Oh, the irony

By barring naturalized citizens from the presidency, the requirement of being a natural born citizen, as Justice Story explained, protects the United States from "ambitious foreigners, who might otherwise be intriguing for the office; and interposes a barrier against those corrupt interferences of foreign governments in executive elections, which have inflicted the most serious evils upon the elected monarchies of Europe."

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