Social Credit's popularity reached its zenith around the time of the East Coast Bays by-election.
Voting resulted in the election of Knapp, the candidate of the Social Credit Party. That was unexpected, as minor parties rarely won seats in Parliament at the time, but such voting was more likely in a by-election. Muldoon blamed Brash and the party organisation for the defeat but was strongly rebuked by the party for the stance. The loss of the by-election provided the catalyst for growing opposition within the National Party to Muldoon's leadership.