In the first instance the question is patently absurd: The President can still be shot so long as guns fire bullets - although given how much security there is surrounding POTUS nowadays you would be unlikely to get an unwarrented photograph, let alone empty a bullet into his brain... or maybe that's just for Bush. (And no obvious jokes about how Bush doesn't have a brain in which to plug a bullet plz! :straightthumb
In the second instance, how likely it actually is, very much open to debate. There could be a
genuine Lone Assassin case - it is unlikely that there would be a "co-ordinated" attack on Obama by the people you'd think would do so; having looked around to find out what people at Stormfront or Aryan Nation seem to think or feel, you kind of get the impression that they consider a McCain Presidency more of an affront to their whole schtick than an Obama Presidency.
One of the sites I saw had a thread about the injustice that saviour of the white man is, in fact, a nigger. (But it was shot down and attacked several times, for some very good reasons - even for racists).
@Ixis: come on man you know the president only gets a crowbar (or an umbrella).
No. He can fight back with Saddam's WMDs: invisible, so they'll never see them coming.