Being Cordial Also An Important Presidential Duty

In the day to day duties of the presidency, there are many distasteful requirements. Not the least of which is having to deal with and smile at people that you don't like, even detest. So my question is simple. Senator McCain, if you cannot shake the hand of Barack Obama, what will you do when you have to shake the hand of Vladimir Putin or "Dear Leader"?

At the end of the second debate, I saw McCain pat Obama on the shoulder to get his attention, and then when Obama turned around and stuck out his hand McCain just smiled and walked away. Not very presidential, I think.