I'll start with the caveat that typing public figures is always problematic due to the contextual nature of their behavior. Having said that, I believe we're looking at a pair of _SFP types here -- ISFP for McCain; ESFP for Obama. The justification for this opinion can be found in this article:
Political Types | Type Insights
PS: For those who need to know what qualifies me to express this opinion -- I'm a Qualified AND Certified MBTI Professional; I've been using multiple models of personality type professionally for over 15 years; I'm Past President of the Los Angeles Chapter of the APT; I've presented sessions on type at many international conferences, including the most recent APT Conferences in the US and Australia.