Original sentence: John Charles Frémont (January 21, 1813 – July 13, 1890), was an American military officer, explorer, the first candidate of the Republican Party for the office of President of the United States, and the first Presidential candidate of a major party to run on a platform in opposition to slavery
Edited sentence: John Charles Frémont (January 21, 1813 – July 13, 1890), was an American military officer, explorer, the first candidate of the Republican Party for the office of President of the United States in 1856, and the first Presidential candidate of a major party to run on a platform in opposition to slavery as a Radical Republican in 1864