Such an interesting question: Is Senator Clinton disqualified under the U.S. Constitution from serving as Secretary of State under President Obama. At least I find it interesting. According to Section Six of Article One in the constitution No Senator or Representative may take a job in the Executive branch if the salary was increased during the time in which you were elected as a Representative.
Well guess what the pay for Secretary of State was in creased in January 2008. But this isn’t the first time. It was also done by Presidents Taft, Nixon, Carter, and Clinton. They typically apply the Saxbe fix (named after Senator William Saxbe who was appointed Attorney General under Nixon) in which Congress lowers the pay back to where it originally was? But, is this an issue that would come up during confirmation in front of all her Senate colleagues? Would an anti-Hillary person sue over this?
I don’t know, but I find it fascinating.
You can find more information on this on the Volokh Conspiracy blog.