Just wondering

I've been wondering about something that's almost unthinkable, but, unfortunately, not completely outside the realm of possibility. Suppose Obama wins the election and the electoral college has voted for him. Suppose he is then assassinated before Inauguration Day. Given the current tenor of the McCain campaign, with supporters shouting "kill him" about Obama, I think we have to at least consider that as a possibility. So, who becomes president? Biden? McCain? Bush? Cheney? Does the House have to vote for a successor? If so, do the Dems have the guts to elect a Democrat? Or, will they bend over backward to be fair and select McCain because he came in second? After all, think about the Republican noise machine and how it will be in full gear if that happens.