Is It a Crime To Trade a Senatorial Appointment Decision for a Cabinet Job?

The charges against Illinois Governor Rod Blagojevich are extremely serious, and much of them allege garden variety corruption, albeit on a massive scale. But I wonder whether one of the items should indeed form the basis for a corruption prosecution:

Rod Blagojevich has been intercepted conspiring to trade [his decision to appoint someone to] the senate seat [vacated by the President-elect] for particular positions that the President-elect has the power to appoint (e.g. the Secretary of Health and Human Services).

It's true that a cabinet position has a salary attached to it, which I believe is somewhat larger than that of the Governor of Illinois. And I agree that trading a decision to appoint someone a Senator for a pot of money is classic criminal bribery.

But my sense is that political deals of the "I appoint your political ally to X and you appoint me to Y" variety are pretty commonplace, though perhaps done with more subtlety than seemed to be contemplated here. Should these deals indeed be treated as criminal bribery? Have they generally been so treated? What if the deal didn't involve appointment-for-appointment swaps but vote-for-vote swaps or vote-for-appointment swaps — e.g., "if you vote the way I want you to vote, I'll vote the way you want me to vote" or "if you vote the way I want you to vote, I, the Speaker of the House, will make sure that you're appointed to the committee chairmanship you always wanted" or "if you solidly support me during this Congress, I'll appoint you to the Cabinet"?

Here this proposed deal seems part of a broader pattern of corruption (though this also means that the prosecution would likely do just fine if they had excluded the deal, and focused on the prospect of trading the appointment for a private-sector position). But the government's theory, I take it, would apparently treat such a deal as a federal crime — assuming the federal jurisdictional requirements are met — even if it were a standalone deal by an otherwise uncorrupt official. So that, I think, makes it worth considering how the law should treat these sorts of deals involving political appointments.