The election was complicated by the Petrov Affair, in which Vladimir Petrov, an attache to the Soviet embassy in Canberra, defected amidst a storm of publicity, claiming that there were Soviet spy rings within Australia. Given that the 1951 election had been fought over the issue of banning the Communist Party of Australia altogether, it is unsurprising that such a claim would gain credibility.
Evatt took the extraordinary step of publicly assuring Parliament, just prior to the calling of the election, that he had written to Vyacheslav Molotov, the Soviet Foreign Affairs Commissar, regarding Petrov's allegations, and that Molotov had assured him that there were no Soviet spy rings within Australia. Menzies was able to use this very effectively in the ensuing election campaign, and Evatt (and the ALP) were defeated, although they made up ground on the ruling Liberal/Country Party coalition.
The defeat, as well as Evatt's many tactical mistakes, led directly to the Australian Labor Party split of 1955, with the Liberal/Country Party coalition retaining power for the next 17 years.
Prior to 1984 the AEC did not undertake a full distribution of preferences for statistical purposes. The stored ballot papers for the 1983 election were put through this process prior to their destruction. Therefore the figures from 1983 onwards show the actual result based on full distribution of preferences.