A 250th anniversary flag on the Dwight D. Eisenhower Executive Office Building, location of the vice president’s office, on 17th Street NW in Washington, D.C., on Tuesday, May 5, 2026. (Photo by Ashley Murray/States Newsroom) WASHINGTON — Parties, protests, displays of historic documents, odes to the Founding Fathers — and a massive political rally by the president — will mark a deeply polarized nation’s 250th anniversary on this Fourth of July.…