Johnston was the only Labor member for a farming seat after 1914, and he was greatly angered by Scaddan's failure to honour a promise to lower the price of crown land.

Under the assumption that Johnston would support the censure as amended, Troy resigned as Speaker in order to give the Labor party sufficient numbers to defeat the government.

However at the last minute Wilson and the leader of the Country Party Francis Willmott persuaded their followers to accept Johnston's nomination as Speaker.

Johnston was forced to suspend the sitting, and the following day he resigned as Speaker, to be replaced by former leader of the Country party James Gardiner.

[2] Johnston resigned his Legislative Assembly seat on 3 October 1928, and on 17 November was elected to the Australian Senate for the federal Country Party.

He fathered three daughters, one of whom married David Wordsworth, a future member of the Western Australian Legislative Council.