When did U.S. political parties first develop party platforms at their nominating conventions? July 18, 2020 by Pamela Landy The first party platform was negotiated by the Democratic Party for the 1840 election. Related Answers How many times have the major political parties held their national conventions in Los Angeles? Who were the first women to head the two major political parties in the United States? What was the first political party in America? How did the phrase Upside Down develop? What was the second country to develop atomic weapons and when did it do so? How did the elephant and donkey come to be the symbols for the Republican and Democratic parties?