As others have noted, Obama rallies are not happy events. Neither is the Obama campaign. There is an angry tone, a desire for revenge against those who supposedly have done the people wrong, a settling of old scores. While Obama preaches hope, the "subtext" of his campaign is anger and frustration. For all the times I have seen Obama on television, only once or twice have I seen him laugh.
A vote for McCain/Palin is a vote for people who are happy -- in their lives, their families, their country. A vote for Obama/Biden is a vote for angry people. You choose who you want running this country for the next four years.