Walsh became a leader in Democratic Party politics in Helena and attended numerous local, county and state conventions as a delegate. He was defeated in a 1906 election for the United States House of Representatives and a 1910 race for the U.S. Senate. Walsh was a delegate to the Democratic National Conventions of 1908, 1912, 1916, 1920, 1924, 1928, and 1932. He was the permanent chairman of the 1928 and 1932 conventions.