Here's what I understand about McCain and abortion. He's generally been a solid but silent pro-life vote. He votes consistently on the pro-life side but has never taken to the floor to advocate for a pro-life bill and has in fact often taken steps to prevent pro-life legislation from making it out of committee. He's not perfect by the right to life crowd's measure.
However, if this issue matters and one's vote turns on it and one is pro-life there's no other choice. Obama is so far to the left on this one its embarassing to him. He's called people who noted his record liars (though he's since retracted those statements when presented with the facts). He voted against a bill in the Illinios state legislature that would have mandated medical treatment for babies born after botched abortions....
http://www.factcheck.org/elections-2...fanticide.html
The link addresses a charge that Obama supports infanticide - which he of course does not - however - its a hairsbreath away. Denial of treatment in the cases at issue will result in death. There is no intentional act causing a babie's death but there is puposeful neglect causing it. At criminal law that'd be called depraved heart or some such thing... and form the requisite intent for a jury to find a crime having been committed.