MacNaughton served as the Canadian ambassador to the United States from 2016 to 2019; he succeeded Gary Doer and presented his diplomatic papers to U.S. President Barack Obama on March 2, 2016.

At the federal level, he spent six years as a senior advisor to Don Jamieson,[5] successively Minister for the Government of Canada's Departments of Transport, Industry and Foreign Affairs.

[6] A longtime Liberal Party of Canada activist, MacNaughton has been involved federally in numerous election and political campaigns.

[9] In 2015, MacNaughton served as Ontario co-chair for the federal Liberal campaign that was successful in electing Justin Trudeau as Prime Minister.

Noble has worked for the Ontario Progressive Conservative Party for several elections, notably as co-campaign manager with Tom Long on the "Common Sense Revolution" which won majority governments in 1995 and 1999.