Two years ago Malcolm Turnbull replaced Tony Abbott as Liberal leader and Prime Minister. But as the Labor opposition queried this week, was it worth the change?

The PM has been the incredible shrinking man since then, becoming increasingly smaller in our estimation as he has discarded most of the values that had initially convinced us to hold him in high regard.

Malcolm Turnbull rose to role of Prime Minister on a tide of goodwill from Australian voters.

He promised economic leadership, an end to the mindless slogans that were the favoured political artillery of his predecessor, and that he would respect the intelligence of voters.

Yet even before he’d been sworn in, Mr Turnbull insulted our intelligence by abandoning his principles. He consciously thwarted the case for gay marriage by striking a new Coalition deal with the Nationals that retained a national vote on the issue. He also cruelled any chance of meaningful climate action by promising the Nationals he would not introduce a price on carbon.

Those troubling disappointments have been followed by many others: a mercifully short-lived thought bubble on letting the states levy income tax; the tone-deaf insistence that tax cuts for big business would pass the pub test in a world where fairness overrides economics; a misguided eight-week election campaign made even more mind-numbing with meaningless slogans like “jobs and growth”; and further capitulation to the right on gay marriage and energy policy.

And then there’s the collaboration with the self-described heir to Tony Abbott’s conservative mantle, Immigration Minister Peter Dutton, who Turnbull has elevated to Grand Poobah of Border Protection, seemingly in return for fending off any Abbott renaissance.

The sad fact is that much of this could just as easily have happened if Abbott had remained as PM.

There are several things however that have happened on PM Turnbull’s watch that wouldn’t have occurred without that coup two years ago.

We wouldn’t have seen a boost in the number of Coalition women in cabinet, a big-spending budget like the one brought down this year, or the level of funding the Turnbull government has delivered for education and the National Disability Insurance Scheme.

Granted, these “achievements” would pale against anything Labor would likely do in government, but they are a considerable step up on what Abbott would have done instead.

So it could be argued we should be a little grateful for the small mercy that was Turnbull’s return to the Liberal leadership in September, 2015.

Of course, Labor supporters would prefer to think that if Abbott had remained as Liberal leader, Australia would have a Shorten government by now.

It’s undeniable that Turnbull has been a disappointment, not just for failing to deliver the truly Liberal, Menzies-style government he promised on the day he challenged Abbott, but for retreating on many of the issues he once claimed to champion.

It’s also true that many other prime ministers have gone on to win elections after being deeply unpopular at the beginning of a parliamentary term.

But there is a difference between being unpopular for doing unpopular things, or even being caught in a lie, and being unpopular for breaching faith with voters.

That is Turnbull’s problem. And given the course he’s currently plotting to walk away from a clean-energy target, the PM’s problem with voters will be compounded.

As a result, the incredible shrinking Malcolm will continue to diminish – until he vanishes completely next election day.