After an education at Christian Brothers College, Walsh left school at fifteen to work as a stonemason, which sparked his interest in the trade union movement.

The LCL, led by Sir Thomas Playford, ruled South Australia through a time of strong economic development and held power thanks to an electoral malapportionment known as the Playmander, in which rural areas were significantly overrepresented in the legislature.

By this time, many South Australian Labor politicians had despaired of ever winning power, and considered the Deputy Opposition Leader's post to be a thankless, low-paying job.

He followed O'Halloran's lead of preferring co-operation with the LCL to criticizing them and maintained friendly relations with Playford, who treated him in a somewhat avuncular manner.

Knowing that the Playmander made a traditional statewide campaign impossible, he decided to focus on targeting the LCL's marginal seats.

Walsh lobbied the Governor, Sir Edric Bastyan, to appoint him Premier instead, arguing that he had won a clear majority of the popular vote.

His term as Premier was marked by increased spending on public education and the implementation of far-reaching social welfare and Aboriginal Affairs legislation, although many of these changes were spearheaded by his deputy and Attorney-General, Dunstan, by far the youngest member of the cabinet (he was the only minister under 50, and one of only three under 60).

Combined with a sagging economy and poor polling figures, local ALP heavyweights concluded that Labor could not be reelected with Walsh as Premier.

Knowing that they had, at most, two years before the next election, SA Labor heavyweights concluded they had to move fast in order to change their fortunes.

After initially digging in his heels, Walsh eventually announced his retirement two weeks later, but not before attempting to manoeuvre Corcoran into the Premiership ahead of Dunstan.

Considered "kindly, generous and unpretentious" by friend and foe, Walsh was praised for his long parliamentary service and his support for unionism and working-class families, but he would frequently infuriate fellow party members by habitually becoming obsessed with trivial issues to the detriment of major policy concerns.