David MacNaughton will return to the private sector in Toronto, where he has held a number of roles before his appointment in March 2016. Kirsten Hillman, currently deputy ambassador to the U.S., will serve as interim ambassador. (Globe and Mail)

Talking point: MacNaughton played a key role in the renegotiation of the North American trade deal between the U.S., Mexico and Canada, and has spent recent months trying to get the U.S. House of Representatives to ratify the agreement, which the House Democrats continue to hold up. His departure means the top jobs in both the Ottawa and Washington embassies are empty—U.S. Ambassador to Canada Kelly Craft was confirmed as Donald Trump’s UN ambassador in July. MacNaughton is an influential figure in Justin Trudeau’s Liberal Party. The former lobbyist and banking executive was Ontario co-chair of the 2015 election campaign and mentored the prime minister’s aides, Gerald Butts and Katie Telford, when the three worked for the Ontario Liberal government of then-premier Dalton McGuinty. MacNaughton won’t have an official role in this year’s election, but he said Thursday he’s available to the PM to provide advice and counsel at any time.