(CBS News) BILOXI, Miss. - The four main candidates for the Republican nomination for president say they're committed to staying in the race right up to the convention this August in Tampa, Fla. There's just one problem: If they do, it might turn out that no one gets the number of delegates needed to win the nomination outright. Stumping in Birmingham, Alabama, Mitt Romney continued his Southern charm offensive, celebrating an endorsement from the country band Alabama. "Wouldn't you love to hear them sing 'Sweet Home Alabama'? Wouldn't that be wonderful?" he asked a crowd at one campaign stop. In...