The modern political convention probably originated in 1984, when Democrats, wary of the fallout from Ted Kennedy having challenged Jimmy Carter to a floor fight at their 1980 convention in New York, implemented a system of superdelegates to ensure that disputes about the nomination process could be resolved by party elders long before they hit the convention floor, allowing the conventions to serve principally as four-day advertisements. It didn't do much good for their nominee that year, Walter Mondale, who received only a two- point bounce from his convention. But other candidates have used the new, news- free convention to better effect. George H.W. Bush got better than a 15-point bounce from his convention in 1988, and Bill Clinton's bounce in his 1992 campaign was enormous. In fact, while the convention bounce usually fades-- often after mere days--it does serve as a litmus test of the enthusiasm for that candidate. Since 1984, the candidate receiving the larger convention bounce has also won the popular vote.
Click Here For A Graphic Illustrating Past Convention Bounces