A candidate will often say that he was in the race to make sure that his ideas were heard. It's a safe way to admit that there was no chance in Hell of winning but that his ego demanded that he try. Occasionally those candidates will help steer their party for better or worse.
Then, on the other hand, you get the vanity candidates. They are the fringes of any race, attracting vocal dedicated loyalists and making the rest of the country go, "Huh?" These candidates stumble along for weeks and months and have all of the impact on their parties that David and David had on music in the nineties.
Ored Dalton Thompson, he of the bastard child, the jilted high-school sweetheart, the man Nixon thought was so dumb that he'd be a help on the committee, and now of the vanity campaign has withdrawn. He'll be back in Hollywood by the end of the week, working out his next movie deal and forgotten when Charlie needs to natter against the liberals out west.
I leave you with Macbeth. "...a tale told by an idiot, full of sound and fury signifying nothing."