He held posts in the administrations of reform mayors Walter Flower and Paul Capdevielle.
McShane ran for a city council seat in 1912 under a 'good government' platform, but lost.
In the election of 1920, McShane was the mayoral nominee of the reform-oriented Orleans Democratic Organization.
The endorsement of reform governor John M. Parker helped him narrowly defeat the incumbent Old Regular mayor, Martin Behrman.
He and his administration were hampered by inexperience at city government and by dissension between various factions of his supporters.