Why holding a presidential nominating convention in a swing state matters

This week the media’s narrative shifts from Cleveland Ohio, the site of the 2016 Republican National Convention, to Philadelphia, Pennsylvania, where the Democrats are holding their convention. That nominating conventions provide a ‘bump’ in the polls for a party’s candidate is relatively well known – but is there an effect on the states and cities which are holding them? Research from Christopher B. Mann and Joseph E. Uscinski shows that party conventions can swing voters in nearby counties, which can in turn shift the statewide outcome in a close contest. Both parties, they write, get an electoral boost from nearby counties that heavily lean towards them, but can experience a polling backlash in counties which support the other side.