Complex sentence: Diefenbaker's failure to have a French speaker as one of his nominees reportedly hurt him with Quebec delegates who held a meeting and considered supporting one of Diefenbaker's opponents en masse, of which Fleming hoped to be the beneficiary.
Split into simpler sentences: Diefenbaker's failure to have a French speaker as one of his nominees reportedly hurt him with Quebec delegates. They held a meeting and considered supporting one of Diefenbaker's opponents en masse, of which Fleming hoped to be the beneficiary.