As its cherished narratives on budgetary and economic management have crumbled under the weight of two tough years in office, the Abbott government has increasingly found its line of attack limited to a narrow frontage of issues on which the public remains receptive to its message.

Every indication is that the resulting diet of national security and terrorism is failing to provide the government with a sufficient foundation on which to build a second election victory, lacking as it does a direct engagement with voters’ hip-pocket concerns.

However, that’s certainly not to say that the government has had no success in its crude objective of wedging Bill Shorten, as demonstrated by the particularly confused account the Opposition Leader has been giving of himself over the past few weeks.

Each time the government has moved to ratchet up terrorism laws, deter asylum seekers and pursue military interventions, Shorten has been made to choose between alienating liberal sentiment in his own party and exposing himself to government charges of “softness” and captivity to the left.

His responses have been nothing if not consistent, with the clear priority on each occasion being to leave as little daylight as possible between his own position and the government’s.

Following Border Force’s infamous announcement of a planned crackdown on visa fraud on the streets of Melbourne a fortnight ago, the worst Shorten could think to say in his initial response was that the government probably wasn’t “fair dinkum”.

Only after the operation was cancelled, and Tony Abbott forced to stress that what the press release appeared to propose was “the sort of thing that would never, ever happen in this country”, was Shorten emboldened to sharpen his rhetoric.

Labor’s lock-step position with the government on military action in Syria has also involved sacrificing an opportunity to exploit community scepticism over the value of foreign entanglements, particularly given the fertile ground for cynicism offered by the government’s efforts to elicit an invitation from the United States.

None of this has made an immediate difference to opinion polls over the past few weeks, which have found Labor consistently maintaining leads of around 53-47 to 54-46 on two-party preferred.

While that might seem to suggest that the public has called a nil-all draw on the bipartisan blundering that has unfolded over recent weeks, closer examination of poll numbers tell a more particular story.

A fortnight ago, I wrote here that the cloud over Dyson Heydon at the Royal Commission into Trade Union Governance and Corruption had translated into higher approval ratings for Shorten, as voters revisited negative impressions formed after his appearances before the commission in early July.

This was evident in polls conducted at the time by both Newspoll and Fairfax-Ipsos, with the former recording Shorten’s approval rating as increasing five points to 34%, with disapproval down five to 52%.

However, Newspoll this week had his approval back down to 30% — equal with Tony Abbott’s dismal rating — and his disapproval shooting up to 58%. Similarly, leadership ratings from this week’s Essential Research poll offer no indication of improvement for Shorten from his low point of a month earlier.

In explaining the mystery of how Shorten’s battered personal standing has failed to have any impact on Labor’s share of the two-party vote, we need look no further than the ongoing ascent of the Greens.

According to the poll aggregate featured on my blog The Poll Bludger, the primary vote for the Greens currently stands at an all-time high of 14.5% — which would, if replicated at an election, be without modern precedent for any minor party.

In other words, the haemorrhaging of support for Shorten over the past fortnight appears to have been concentrated on the left, where defection to Tony Abbott is not an option.

Even so, it’s clear that the reputation for hollowness and indecision that has been the price of Shorten’s small-target approach is not quarantined to the one side of the ideological fence.

Next Saturday’s byelection in Canning accordingly carries only slightly less danger for Shorten than it does for Abbott — particularly if reports of growing Liberal optimism for a reasonable result prove to be on the money.

A precedent that may be keeping Shorten awake at night is that of former opposition leader Bill Hayden in December 1982, when he faced a byelection at a similar point of the electoral cycle in the Victorian seat of Flinders.

As a deep recession sent the unemployment rate soaring towards double figures, Labor was only able to bite off half of an existing Liberal margin of 4.6%, signalling to powerbrokers that a change at the top was needed if the party was to be fully confident of toppling Malcolm Fraser at an election due the following year.

Happily for Bill Shorten, though perhaps not the Labor Party more generally, one key element in this scenario is lacking from the current picture — a leadership rival of the stature of Bob Hawke, who within three months would fulfil his self-perceived destiny by displacing Hayden and leading Labor to victory at the snap election that followed.