She may be Constitutionally ineligible. Sometimes commenter Jane Bernstein notes via email that Article 1, Section 6 clearly states that:
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.
Emphasis mine. Federal salaries, including the schedule for a Level 1 Cabinet officer (such as Secretary of State) were increased at the beginning of the year, by executive order. IANAL, but by the letter of the law, it would seem that she cannot be appointed to that position.
There are two potential outs.
One is trivial–she isn’t a “he,” she’s a “she,” so she could amusingly argue that the section doesn’t apply to her. I suspect that this would probably fail on Fourteenth Amendment (and perhaps other) grounds, though, as well as common sense.
The other would be to argue that the intent was to keep Congress from creating or increasing salaries of a position in order to provide a new or better job for one of its members, and to eliminate this potential conflict of interest. Since the increase was done by Executive Order under a previously passed law, she could argue that Congress didn’t increase the pay in this instance. However, the letter of the law wouldn’t allow this interpretation–it doesn’t say anything about the emoluments increasing by act of Congress–it just says that if they increase (for whatever reason) she cannot have the position.
If true, the good news is that it would also apply to John Kerry. And it doesn’t apply to Barack Obama, since he wasn’t appointed–he was elected.
[Update a few minutes later]
Also, if the logic is correct, it would apply to Rahm Emmanuel, as well as any other potential congressperson or Senator angling for an appointment.
[Update on Monday afternoon]
More thoughts from Eugene Volokh.
[Bumped to the stop]