It was June 26, and the man who had been among the most pivotal in the removal of Kevin Rudd three traumatic years earlier – earning him the "faceless man" tag – was again pulling the pin.

Like the Jamie Lannister character from Game of Thrones, who killed one to save many, the mantle of "Kingslayer" would never sit well on his shoulders, no matter the justification.

It was a simple equation, yet diabolically complex.

Shorten had already been spoken of as the most likely contender for the future leadership and wanted desperately to keep his hands clean.

After six shambolic years, only the foolhardy believed another leadership change would result in any electoral favour, so Shorten, like others, was already looking beyond a grim polling day to the rebuilding phase.

Assuming his abandonment of Gillard did not itself kill off his career, the simple fact of a second Labor PM being torn down in as many terms threatened to render Labor morally and electorally bereft.

A trainwreck loomed, no matter which way you looked at it, said one MP in the days after.

As Shorten wrestled with the issue, his every word parsed by a baying media pack, all looked for signs of a switch back to Rudd. It came as the fatal blow.

"It was an incredibly hard decision, a place you never want to be in," he told Fairfax Media in an exclusive interview marking his first year as leader.

"But it was about, for me, that Australia needs a strong Labor party, millions of people count on us, so it was a matter of making decisions to ensure the Labor party was ready to rebuild after the election – and we have been."

This is politics, where the natural cynicism of Australians runs deepest, so Shorten's betrayal of Gillard, irrespective of her unpopularity, had confirmed that cynicism. He might well have been doomed there and then.

Sixteen months later, however, it's a different story.

By any measure, Shorten is in a good place – for an opposition leader, that is. Which is not to say he will win the election in 2016, or even that he will improve significantly on the 2013 result.

But his supporters in the Labor caucus – and that means almost everyone – are not complaining.

Nothing sells like success and Shorten, surprisingly, offers some chance of that.

This is a remarkable outcome given the depths of the fall. Labor's primary vote had slumped to just 33 per cent at the September 2013 election – it had not been lower in three quarters of a century.

It lost an AFL team of MPs as voters deserted the party in emphatic fashion.

Which makes Shorten's path out of the morass at the head of the bedraggled Labor peloton all the more Phoenix-like. In fact it was the fastest transition  from an election loss to a poll lead over a new government in the history of the Fairfax-Nielsen poll series.

The story of that rise is also the story of the Abbott government's failure via the political gift that keeps on giving, Treasurer Joe Hockey's first budget.

Such is the see-saw of Australian politics that a poorly orchestrated pre and post-budget sales job has sent the government's stocks plummeting and sent Labor's trending up.

But an unpopular government struggling to justify broken promises is not the only factor in Shorten's healthy poll lead.

Like a constant background hum that you only realise has stopped when it is pointed out, Labor's toxic culture of perennial division has suddenly gone quiet.

MPs say Shorten regularly points this out at Caucus meetings as part of his message to his charges to stay positive and keep their guns trained on the government.

Yet outwardly, the "new normal" of unity has almost escaped mention.

Ironically, this improvement is mostly down to Rudd, perhaps the most polarising and divisive Labor leader since Billy Hughes, because it was he who drove through the reforms just before the last election that make it practically impossible to turf out an opposition leader.

The impact has been transformative, and a boon for Shorten, who perhaps because of his past centrality in leadership changes understands the value of it.

"I don't underestimate the impact of not fighting amongst ourselves so that we can fight for people," he says.

Rising star Jim Chalmers credits his leader with the result as much as the rule.

"Bill's been a unifying force," Chalmers says, lauding Shorten's people-management ability.

"His capacity to bring people together is probably our greatest asset.

"The fact we're competitive again, so soon after a devastating loss, speaks to the way he's given focus and direction.  People would take two things from his first year: that he's got us singing from the same song sheet, and that he's standing up for middle Australia against an awful budget."

The "people management" contrast with Rudd is most stark. Where the former PM surrounded himself with 20-something whiz-kids – effectively as a bulwark against challenging advice – Shorten recognises his limitations and seeks to augment them with the right people.

And while the now 47 year old would be young for a prime minister in the unlikely event of a single term in opposition, he maintains he is ready.

It's a live question given that there is a valid critique of failed Labor leaders, from Mark Latham to Kevin Rudd and Julia Gillard, that none had even sat around the cabinet table before heading their party. It is this experiential gap that proved fatal. Shorten feels he's done his time as a minister and is growing every day as a leader.

Asked if he is ready to be prime minister, he hesitates, before answering firmly that he will be.

Shorten prefers to leave the assessment of his performance to others, but admits he is quietly pleased with where he is at present. He says unity was an absolute prerequisite for getting people to listen to Labor and has therefore been the year-one priority. Year two and beyond will turn on how he can leverage that unity to re-establish trust with a bruised electorate. Crucially, this will involve repairing a badly damaged relationship with business – an implicit acknowledgement of past Labor failing.

It hasn't been all smooth sailing, though. A long-running and unsubstantiated rape allegation dating back to his days in Labor's youth wing surfaced this year, culminating in a police investigation before it was determined that  no charges would proceed. Shorten outed himself as the subject of that investigation, clearly relieved it was at an end. Yet it hasn't gone completely.

The Abbott government's royal commission into union corruption has also ground on, with an extension granted this week, and it will report on Shorten's old union the AWU, inter alia, closer to the election.

Doubts linger also over the Labor leader's real commitment to party reform, with critics saying he has done little to genuinely democratise and limit the pernicious influence of big unions within the ALP.

Through all of this Shorten has remained remarkably cheery. Even a steady stream of legacy protecting books by Labor figures has failed to dent his mood. Asked whether such commentary has made his job more difficult, especially the necessary catharsis of admitting past mistakes, Shorten was philosophical, declaring his job was not to be "historian in chief" but to look to the future.

Yet for all his professed positivity, Labor is yet to square up to its serious errors, and has failed to put much of substance on the policy table. In fact, with the exception of his support for the Iraq campaign and certain draconian counter-terrorism laws which frankly deserve more scrutiny than he has afforded them, Shorten has if anything, adopted the grindingly oppositionist stance of his foe, Tony Abbott.

It is a fact that drives Liberals spare. Whereas Abbott earned the moniker, "Dr No", Shorten has been just as negative as opposition leader, refusing to pass large swathes of the budget for example, while getting away with it.

There is a sense, also, that the opposition leader is coasting, propelled along as much by the tail wind of voter resentment towards the government, as by anything he's doing.

Then there's the unavoidable obstacle course ahead.

Entering the mid-point of this term, voters will be looking for signs that Shorten has the policy rigour, the imagination, and the answers to a complex array of problems.

Principal among these is the budget challenge, or what Abbott and Hockey have called a "crisis".

Labor's blunt rejection of some $33 billion in savings is politically expedient in the short term because the items being blocked are all unpopular, and are mostly based on broken promises. But the move does nothing in the longer term to address what is now becoming clear is a chronic, permanent revenue shortfall.

This is a real problem and one which threatens to get worse with time.

Money not available to the government in the budget approaching 2016 will also not be available to the opposition to fund its proposed program. And with fiscal management a major weakness of Labor's reputation, Abbott and Hockey will be quick to tie the blame for a deficit – and the fear of worse if Labor is elected – to Shorten's intransigence.

When John Howard was asked what he wanted for Australians, he said for them to be "comfortable and relaxed".

Shorten's version? "I want Australia to reach for higher ground," he says, "to be open to the world, open to its markets, open to trade, open to competition, open to productivity, but with the strongest possible safety net to ensure that all Australians can get a chance to be somebody."