It was held during World War II, and five of the largest political parties – Conservative, Labour, Liberal, National Labour and National Liberal agreed to an electoral pact not to contest any by-elections in seats held by any of the other parties.
The British Union of Fascists (BUF) had contested several recent by-elections, receiving very few votes.
Haslam had served in France and Palestine during World War I and had won the Military Medal at the Somme.
When Mosley spoke in Middleton and Prestwich, he was attacked with missiles and some attempted to hit him.
The government was also preparing to make the BUF illegal under wartime powers, and arrested several Fascist activists in the run-up to the election.