Just watching the DNC convention last night and noticed that the Dems have the opportunity to reply to specific statements made by the Republicans, because they are doing their convention second. It seems to me that having your convention last is a large advantage, but what do I know? Do the two parties try to out maneuver each other in setting the convention date or do they have a tradition for how they do it?
The party of the sitting president customarily gets first choice, and chooses to go last so its own message has more opportunity to sink in. Both conventions are scheduled around the Olympics.
They check the weather forecast months in advance, of course.
This wasn’t always true. The Democrats almost always went last. It changed in the television age, though, so incumbent party goes last has been true for the adult lifetimes of the vast majority.