In the 1940 election, she was defeated. With the death of United Reform MP for Saskatoon City, Walter George Brown, a few days after the election, Macphail was recruited by the United Reform Movement to run in the by-election to fill the seat. On August 19, she was defeated by Progressive Conservative candidate Alfred Henry Bence. He received 4,798 votes, while Macphail placed second with 4,057 votes. It was her last federal campaign as a candidate.