lcpiper, I understood Bill Clinton's charisma. I don't understand Barack Obama's. So, while I know what you mean by unmistakable charisma, I don't personally see it.
What I see, personally, is a lot of people who want to see charisma, where what I see is a guy who acted like an 8th grader during debates (making faces, looking at his watch, etc) and who generally acts as though he believes he is smarter than anybody with whom he comes in contact.
I guess some might actually find that charismatic; I do not. But I suspect more are projecting the traits they wanted to see in what they viewed as an historic first.