Bill Shorten’s niggling byelection headache following Tim Hammond’s resignation last week has now developed into a full-blown migraine, after another uncompromising High Court ruling on Section 44 triggered mass layoffs in the House of Representatives yesterday.

The latest developments are a serious blow to the credibility of a leader who claimed last year that the government’s “legitimacy and integrity” had been called into question by the Section 44 debacle, while boasting that his own party had been spared by its “strict vetting process”.

Far from being an ordinary political misfortune, this one entails a dangerous dynamic in which Shorten’s immediate discomfort could feed into an electoral humiliation that will not be so quickly forgotten.

Those facing the looming “super Saturday” of byelections are Susan Lamb and Justine Keay, who gained Longman and Braddon from the Coalition on fragile margins in 2016; Josh Wilson, who is rather more comfortably placed in the Labor stronghold of Fremantle; and the one non-Labor casualty, Rebekha Sharkie of the Centre Alliance (yet another rebranding for the Nick Xenophon Team), who holds the usually conservative seat of Mayo.

Covering the north-west of Tasmania, Braddon is a white working class electorate par excellence, boasting the nation’s lowest proportion of high school graduates, its sixth lowest average income, and its second lowest proportion of non-English speakers.

It is also typical of a struggling regional seat in having many more residents in their 50s or 60s than their 20s or 30s.

Transplanted to another corner of the Anglosphere, it could no doubt have shocked genteel metropolitan opinion in its enthusiasm for Brexit or Donald Trump.

Latent populist sentiment could no doubt have been activated if local hero Jacqui Lambie had seized the opportunity for an early comeback, but she has determined, to the great relief of Labor, that there are more headlines to be made as a Senator.

More problematic perhaps is the seat of Longman, which combines the unglamorous outer Brisbane centres of Burpengary and Caboolture with the retirement havens around Bribie Island.

When Susan Lamb unseated boy wonder Wyatt Roy with the state’s biggest anti-Coalition swing in 2016, a contributing factor was One Nation’s direction of preferences to her, a unique circumstance out of the 15 seats the party contested.

Given the unlikelihood of this being repeated, Lamb will probably have to improve upon her 35.4% primary vote if she is to retain the seat.

This will be a particularly tall order among voters at the Bribie Island end, many of whom will have caught the wrong end of Labor’s dividend imputation policy.

Then there are the two byelections in Western Australia, a state that has an electoral life of its own due to the primacy of the GST revenue issue – albeit that the major parties are equally constrained in exploiting it, owing to the thankless zero-sum nature of the revenue sharing game.

It was argued here last week that the Perth byelection was more dangerous for Labor than polling suggested, but the same cannot be said of Fremantle, which has had an uninterrupted run of Labor members going back to John Curtin.

The Liberals are unlikely to contest the seat and, barring a surprise comeback attempt by Scott Ludlam, there is little reason to think the Greens will threaten Labor, contrary to an impression that seems to derive from the party’s win in the state seat of Fremantle in 2009.

The federal seat is a larger and more unwieldy object from the Greens’ perspective, being much less dominated by the bohemian port city that gives it its name.

Perversely, the biggest danger to Shorten may lie in the one seat where Labor will not have a dog in the fight.

Rebekah Sharkie became Mayo’s first ever non-Liberal member when she won the seat in 2016, a feat she achieved at the peak of Nick Xenophon’s electoral powers, and with the aid of a scandal that had cost Liberal incumbent Jamie Briggs his place in the junior ministry.

Sharkie will have a very difficult time matching that performance in the wake of Xenophon’s bruising reverse at the state election in March – particularly if, as seems likely, her Liberal opponent is Georgina Downer, whose father held the seat for 24 years.

Even if Labor scratches out wins in Braddon and Longman and staves off surprises in Perth and Fremantle, the achievement will pale in comparison with the boost the Coalition will receive if, after all the heartache the Section 44 crisis has caused it, the end result is a boost to its parliamentary majority.

Little wonder then that the government is reportedly contemplating pushing the date out to early July, so as to maximise the discomfort Shorten will face at Labor’s national conference later in the month.