Complex sentence: W.A.C. Bennett had foreseen the CCF's argument that it could form government assuming Uphill's support and obtained Uphill's agreement that he would instead support Social Credit's bid to form the government.
Split into simpler sentences: W.A.C. Bennett had foreseen the CCF's argument that, with Uphill's support, it ought to be called upon to form a government. Bennett obtained Uphill's agreement that he would instead support Social Credit's bid to form the government.