Article 1 Section 6 reads:
No Senator or Representative shall, during the Time for which he was elected, be appointed to any civil Office under the Authority of the United States which shall have been created, or the Emoluments whereof shall have been increased during such time; and no Person holding any Office under the United States, shall be a Member of either House during his Continuance in Office.
Hillary was a sitting Senator from NY when bambi tapped her for Secty of State.
Cheers!