The White House did not disclose what those options were, but people briefed on the matter said one option was an appointment to the president’s Intelligence Advisory Board, a panel of prominent Americans outside government who provide independent oversight of the nation’s spy apparatus and advise the president. But White House officials discovered that it would not work because Mr. Sestak could not serve on the board while still serving in Congress.
That's similar to what Karl Rove has been saying since news broke. The reason is that serving in both the Executive and Legislative branch at the same time violates the Separation of Powers.
So, now come the questions. Are we really to believe that a former president and a former Constitutional professor, and current president, didn't know that you couldn't serve in both branches at once? If neither did, what does that say about the competence of both, especially the current occupant of the White House, in handling his duties.
One would think that all involved would know that in order to serve on the White House' advisory panel Joe Sestak would need to give up his Congressional seat. So, now we're supposed to believe that Sestak would give up his bid at the Senate in order to take on an unpaid advisory position that would also mean giving up his Congressional seat.
If the White House wanted to end this matter, they may have wanted to explain the curious logic one would need in order to believe a story less and less believable every single day.