I just saw on Drudge that 3 polls show Obama with a lead over McCain in November. Drudge then shows a beaming John McCain with the caption “Underdog!”

I’m wondering what the general effect of being declared the frontrunner or underdog does to your candidacy. I’m sure there are countless examples of the rule being broken, but what is the general rule?

Do people tend to be attracted to the frontrunner’s success, or do otherwise inactive voters rally behind someone when they think he/she might lose? I’m sure both are true depending on the voter you’re talking to, but there must be a general rule for the voting U.S. population.