He served as legal counsel for a number of labor unions and for several years was a temporary clerk of courts in Middlesex County, Massachusetts.

[1] Walsh was a member of the Citizen's Municipal League and supported James J. Storrow over John F. Fitzgerald in the 1910 Boston mayoral election.

[3] In 1912, he was a candidate for the United States House of Representatives seat in Massachusetts's 10th congressional district but lost the Democratic nomination to William Francis Murray.

[6] He narrowly defeated 1918 and 1919 gubernatorial nominee Richard H. Long to win the Democratic nomination, but lost the general election to Republican Channing H. Cox 67% to 30%.

[9] On January 23, 1934, the Boston Bar Association filed a petition for Walsh's disbarment in the Massachusetts Supreme Judicial Court, alleging that he collected money for a client and failed to account for all of it.