The "racist ramblings" of a man in Colorado posed no threat to Democratic presidential candidate Barack Obama but reminded many Americans of past attempts on the lives of their leaders.

Colorado police seized two rifles with hunting scopes and ammunition from a man they arrested a day before the Democratic national convention opened in Denver.

Many voters recall the 1963 assassination of Democratic President John Kennedy and those in 1968 of his brother, Democratic candidate Robert Kennedy, and black civil rights leader Martin Luther King.