At opposite ends of the world, two labour parties are undergoing very different experiences of public conflict between their heads and their hearts.

In our own corner of the globe, the biggest story to emerge from Labor’s national conference on the weekend was Opposition Leader Bill Shorten’s victory on turning back asylum seeker boats. This was crucial not just to his immediate authority as leader, but also to his hopes of keeping the election campaign agenda focused on the issues that mark Labor’s clearest path to victory.

For all the anguish the asylum seeker issue may cause for the party membership, preferential voting makes it difficult to contest the view of Labor hardheads that votes gained from the Liberals weigh a lot more heavily than those lost to the Greens, whose preferences make it feasible for Labor to score lower house majorities with not much more than a third of the primary vote.

However, the fraying of Labor’s direct support base carries costs that are less immediately apparent, but no less significant for that.

Electoral calculations tailored for the House of Representatives are of little value in the Senate, where Labor’s historically low share of the primary vote has reduced it a tally of 25 seats out of 76 — well below its previous low point since Parliament expanded to its current size in 1984, and without precedent even in the period from 1949 to 1984, when the states had only 10 senators rather than their current 12.

This leaves Labor permanently reliant on the Greens to win contested votes, creating a perception of linkage between the two parties that damages Labor in the eyes of the very constituency that measures like boat turnbacks are designed to appeal to.

A similar paradox currently confronts the Labour Party in Britain, which enjoyed spectacular success for a time after jettisoning its leftist baggage under the leadership of Tony Blair.

However, the resulting sense of disenchantment among much of its traditional support base came home to roost at the election on May 7, when it was all but annihilated north of the border by the Scottish National Party.

Should this realignment prove permanent, Labour could find itself structurally incapable of stitching together a parliamentary majority without the support of the SNP — something that has already been shown to be lethal to it in the decisive electoral battlegrounds of England.

In recognition of its need to re-engage with its base, Labour is pursuing a radically reformed process to choose a new leader to succeed Ed Miliband, which essentially amounts to a straight ballot of not only party members, but also those willing to pay 3 pounds to become a “registered supporter”. This supersedes a system that already limited the parliamentary party to one-third of the vote, the remainder being determined equally by the memberships of the party and affiliated unions.

To the horror of the party establishment, there appears to be a very strong chance that the new procedure will deliver victory to Jeremy Corbyn — Labour’s most rebellious member in terms of his parliamentary voting record during the Tony Blair-Gordon Brown years, and one of the most militant figures left standing under the party umbrella.

As members of the Labour left romantically envision the transformation in British democracy that might result from a return to the party’s socialist roots, Conservatives are arguing the merits of sabotaging the party by signing up to vote for Corbyn — a debate that is concerned purely with the ethics of the matter, since it is agreed that the strategic value of the objective cannot be faulted.

Compared with this leadership election model, the ALP’s 50-50 split between the parliamentary party and the rank-and-file looks remarkably modest.

Tellingly, its debut outing in October 2013 showed up a wide division between the caucus, which went 64-36 in favour of Shorten, and the members, who broke 60-40 for Anthony Albanese.

While factional considerations had much to do with the caucus result, it equally reflected a view that Shorten, who had spent his career grooming himself for the leadership, made for a safer bet than Albanese, a figure of the Labor Left who had chiefly enamoured himself to the rank-and-file through his aggressive performances in Parliament.

The party gatekeepers further revealed their mistrust of the membership’s judgement on the weekend by voting to leave Senate preselections in the hands of the union-dominated and heavily factionalised state conferences.

This entailed the rejection of a reform push to have half the vote determined by a ballot of the members, which had the backing of party elders including former foreign minister Gareth Evans, former treasurer John Kerin, and a brace of ex-premiers, including John Cain from Victoria and Carmen Lawrence and Geoff Gallop from Western Australia.

The membership’s share of the vote in lower house preselections will also remain at 50%, with consideration of a move to increase it to 70% placed on the backburner.

The one new bone thrown to reform advocates involved the composition of the national conference itself. This too had been the exclusive privilege of the state conferences in the past, but 150 out of roughly 400 delegates will be chosen by the membership when it is next held in 2018.

The conference also confirmed that the membership will help determine if Bill Shorten will again front it as the party’s leader, having confirmed the 50-50 leadership election model in the party’s constitution, after previously being purely a matter of the rules of caucus.