If Obama does get the nomination, I think the Clinton Machine would work behind the scenes to defeat him... At McCain's age, he could very likely be a one-term president if he were to win. She could then again run in 2012 against the next GOP nominee. If Obama wins, he would stand a good chance at re-election since normally presidents win two terms if they run. This would put her at almost 70 if she were to run in 2016. They'll work closely to make sure any negatives that come out not be attributed to the McCain campaign, allowing him to denounce any negatives. This would make him look even better in the eyes of voters while the negatives get out there.