Peter Baker provides some further information about what kind of job was offered to Joe Sestak last year:
Rahm Emanuel, the White House chief of staff, asked [Bill] Clinton to explore the possibilities last summer, according to the briefed individuals, who insisted on anonymity to discuss the politically charged situation. Mr. Sestak said no and went on to win last week’s Pennsylvania Democratic primary against Senator Arlen Specter.
The White House did not offer Mr. Sestak a full-time paid position because Mr. Emanuel wanted him to stay in the House rather than risk losing his seat. Among the positions explored by the White House was an appointment to the President’s Intelligence Advisory Board, which provides independent oversight and advice the president. But White House officials discovered it would not work because Mr. Sestak could not serve on the board while still serving in Congress.
....The office of Robert F. Bauer, the White House counsel, has concluded that Mr. Emanuel’s proposal did not violate laws prohibiting government employees from promising employment as a reward for political activity because the position being offered was unpaid. The office also found other examples of presidents offering positions to political allies to achieve political aims.
This explains a lot. The job offer really was a quid pro quo because an unpaid appointment would have been an additional position, not a replacement for his current job, and it was contingent on Sestak dropping out of the primary. And since Bill Clinton was involved, this ends up indirectly involving Hillary Clinton too.
This still strikes me as big nothingburger: presidents engage in political horsetrading all the time. At the same time, it's starting to make a little more sense why everyone has been so reticent to talk about it. Regardless, I still think this is a 2-day story once the White House and Sestak produce more details. A week tops. There's just nothing serious here.