Polls indicated a small bounce for 2008 Democratic presidential nominee Barack Obama after his party 's convention in August , but as expected , much of it evaporated during and after the Republican convention the week following , yielding GOP candidate John McCain a small lead in several polls . Nielsen ratings revealed that year 's party conventions to be the most-watched ever , with the Republican convention narrowly trumping the Democrats ' . The RealClearPolitics polling index revealed the 2012 convention bounces for President Obama and GOP challenger Mitt Romney to be comparably smaller than in past elections . Though Romney pulled even with Obama during that year 's Republican convention at the end of August , Obama opened up a three - or four-point lead during the Democratic convention the week after
Republican convention
2008 Republican National Convention
Convention bounce