I'm not sure more candidates need to announce there. But as a former resident of Philly, I wish the founding documents were kept there rather than being buried in apocalyptical vaults in DC.
I don't know, the security and the upkeep required to keep them in good condition would require the gutting of the building. The Archives are secure and relatively accessible.
I think a good place for a future presidential announcement from a Floridian would be our old capitol building. In fact, maybe if I get to be Governor Putnam's 2028 campaign manager I'll arrange for that
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The backside of the building has wider steps and a sort of plateau in the middle where a podium can fit, and there is enough room between the new capitol and the old capitol to cram in a few hundred people and a media stand for the cameras to broadcast the announcement. It's also overshadowed by the new 22 story capitol so the heat doesn't become an issue, the sun doesn't cause any glares, and the small space makes it easier to exaggerate the crowds size if the event is filmed right.