Ok, so this is an interesting move on McCain's part.
He needs two things right now.
The first is time away from this existing crisis. Since polls are showing that the American citizens see the current financial ills as the Republican's doing, now probably would not be a good time to have a Presidential debate. That is, if you are a Republican.
The second thing McCain needs is some ammunition. He needs to get something on Obama and what better way to do that than to lure Obama into this mess in D.C. This gives McCain the opportunity to watch what Obama does and says. Thus providing him and his staff fodder that can be spun and injected in new negative campaign ads as well as material for debates.
When McCain made this decision to go to Washington and ask Obama to do the same, he placed himself in a precarious position. First off, Obama decided he wasn't going to play. He wants to move forward with the debates. Now that puts McCain in the undesirable position of either A) calling off the debates and looking like a coward or B) eating crow and being forced to debate. He didn't want to have to make either decision.
So, he does the next best thing. He makes it someone else's decision to call off the debates and tells the President to make Obama come to D.C.
Obama was right when he said that Presidential politics have no place being injected into this current situation. And that is EXACTLY what McCain is doing.