Pete Buttigieg speaks at a rally the day before the Iowa caucuses at Lincoln High School in Des Moines, on Feb. 2, 2020. (Photo by Kathie Obradovich/Iowa Capital Dispatch)WASHINGTON — Democratic Party leaders from a dozen states traveled to Washington, D.C., at the end of May to press for their voters to cast the first ballots in the next presidential primary. State representatives argued that diversifying the early states would ensure Democra…