After working as a publisher for some time and becoming part owner of the Chicago Tribune, which his maternal grandfather had owned, he entered politics.

His mother Katherine Medill McCormick hoped that leadership of the paper would pass from her brother-in-law, Robert Wilson Patterson, to her first son.

Joseph Medill McCormick took over much of the management of the paper between 1903 and 1907, but became increasingly depressed and developed alcoholism.

[4] His younger brother, the famed "Colonel" Robert McCormick (1880–1955) became involved in the newspaper, worked closely on it for four decades, and was a leading isolationist figure in the Republican Party.

In the primary election of 1924, McCormick lost the Republican U.S. Senate nomination to Charles S. Deneen, who had previously served as the 23rd Governor of Illinois.