John M. Callahan was an American politician who served as chairman of the Democratic Party of Wisconsin from 1925 to 1927.
[2] In 1910, he lost to incumbent and future U.S. Representative James A. Frear and in 1924, he lost to incumbent a future Governor of Wisconsin Fred R. Zimmerman.
At the convention, his name was put into play for the Democratic Party's nominee for President of the United States.
The nomination eventually went to John W. Davis, who lost to incumbent Calvin Coolidge in the general election.
In 1934, he was a candidate for the United States Senate, losing to incumbent Robert M. La Follette Jr.