Some decisions before him involve the budget that his Treasurer presents in early May, and others the policies that he puts to the public at the next election. Another involves the timing of the election itself, and whether he has much to gain from double dissolution.

Much more important, however, are decisions by which he shows voters a sense of purpose and direction, laying out a path Australians will want to follow. Only by that can he demonstrate that he is still in charge of his, and Australia's, fate. His decisions will show if he has become, as Tony Abbott, Kevin Rudd and Julia Gillard did before him, a prisoner of his past, increasingly unable to control his future.

If Turnbull plays his cards right, he could be prime minister for a long time. If he plays them badly, he could be the shortest-serving real prime minister of the modern era, with less than a year in the job. (Short terms for stopgaps, such as Sir John McEwen and Frank Forde, after prime ministerial deaths, don't count.)

The bigger risk is that he could limp back to power, but with his authority and reputation damaged, relatively easy prey for his many enemies in his own party, vulnerable to Abbott tactics from before and behind. He is not prime minister because his colleagues love him, trust his judgment or believe in what he believes. They suffer him, with varying degrees of enthusiasm, only while they believe he is the one most certain to deliver continuing electoral victories. And a defeated, but strengthened, Labor will have no reason to play nice, even to a person who wants to play hard but fair, by debate rather than eye-gouging.

Three months ago, Turnbull seemed to be comfortably cruising to victory. The public had, for a while, wanted anyone but Abbott, even Shorten.

But it turned out that they would infinitely prefer Turnbull to Bill Shorten, and, for a while, it seemed that nothing that Shorten could do could bridge the gap. But the polls, horizontal and vertical, now suggest that the gap is narrowing. It turns out that Turnbull is not the leader he promised to be. He hasn't been the messiah, and he doesn't even seem to have a gospel.

Voters have not so much warmed to Shorten again, or yet reconciled themselves to the idea that a new Labor would do a much better job. But they are disappointed with Turnbull, if not yet completely disillusioned. Voters understood that there were limits to what Turnbull could do immediately, given the way he had seized power and the promises he had made on the way. They knew he would have to govern for a year with one arm tied behind his back. But it seems clear that they have expected rather more than they have been getting. And that they expected something more than a mere change of style.

After the pseudo-tax debate of the past few weeks, the impression that he is all talk and no action – and that he will fold at the slightest sign of internal party dissension – is taking root. Soon it will be hard to shift.

In the administration, the sense of relief that the Abbott nightmare is over is still palpable. Many are also cheered by evidence of process, calm, consultation, cabinet government and the disappearance of that contrived panic, sense of emergency, tribalism and micromanagement that finally took Abbott out. People already respected Turnbull as a pro, as a thoughtful person, open to reason and argument. But now some are wondering whether he has the ticker to make tough choices. Or the courage to take the electorate into his confidence, the drive and energy, and the audacity, to actually make things change.

Perhaps, some reason, he has become too civilised, too decent, too reflective to take risks, or to make government an instrument of his will. Or perhaps he lacks an immediate agenda, other than remaining in power. No one is yet writing him off, but a few have been astounded by this month's lack of nerve, discipline, and resolution, the more so given that opportunity was beckoning, and a good many people want him to succeed.

Voters may not pay much attention to what policy professionals, "insiders", and the "commentariat" think. Tony Abbott would try to deflect constant attention to his stumbling, and the death watch, by dismissing what he called "Canberra games" or "insider stuff". But there's a lot of it around. Most voters ultimately hear the scores and catch the mood, even when they apply discounts according to their opinion of the commentators. Bad impressions about ticker persist. Ask Kim Beazley.

The image is the more damaging because it comes from both sides of the paddock. The Abbott rump is as happy to say that Turnbull has not changed Abbott policies as Labor is. Not a few Labor-leaning voters with a favourable impression of Turnbull have been disappointed that he has not changed anything much. They are right, he hasn't. He did change the mood, and the static, and the shrillness, but not much is really different.

He had an implicit free hand to deliver better economic management – including more effective action to reduce the Coalition's own ballooning deficits and increased government debt. He helped raise expectations of action to address collapsing government revenue, and there was at least some resigned public consent to some form of tax increase. But he has suddenly veered away. The general state of the economy might suggest that now is not the time to be removing money from circulation. But his party, and even his own old opposition rhetoric, has been fixated upon fear of government debt and deficit, and the need for a plan to bring the budget under control.

Labor, by contrast, has put forward policy proposals for increasing government revenue, while promising restraint on government expenditure. It is seeking to outflank Turnbull and may have already succeeded, given the way in which Turnbull has switched to unconvincing scare campaigns about house prices – just the sort of thing he once promised voters he would not do.

No doubt the budget will deliver spending cuts (concentrated, no doubt, in the out-years). But this week the government announced major new defence expenditure which, even if necessary, can only increase deficits and debts. That the defence white paper might be read as a Labor-style economic stimulus plan, or industry policy – of the sort that free marketers (and the Treasury) once affected to regard as anathema – is interesting, but perhaps not to the point.

The point may be that Labor might credibly present itself to voters at the election as the party which is the more conservative economic manager, the one with a plan to address deficits and debt, and the one more likely to bring the budget into balance more quickly. The Coalition, by contrast, might be credibly painted as the alternative without ideas (other than a default setting of cutting health and education benefits, regardless of promises made) and without the courage and the vision to face the facts, other than with sunny ideas about optimism and innovation.

Some observers might think it a big ask that voters would prefer Labor as economic managers. They certainly don't yet. Abbott and his team did a good job of arguing that the (Labor) tenants had "trashed the joint", creating a "debt and deficit disaster". They derided excuses about revenue shortfalls. They sabotaged and campaigned against both revenue and expenditure measures.

But the truth is that the management of both the budget and the general economy under Labor was generally well disciplined, particularly on the expenditure side. The politics and salesmanship might have been awry – and sometimes the targeting was madness. But the rein was generally tight, not least bearing in mind the strains caused by the GFC. It is unfair to characterise Lindsay Tanner, Wayne Swan, Penny Wong or Chris Bowen as profligate.

The Coalition government has, by now, its own credibility problems on economic management. Abbott's second budget was an abject retreat from the principles of his first. Scott Morrison has changed nothing. The ascent of Barnaby Joyce as National Party leader can hardly augur well for tighter or more focused fiscal discipline.

The Coalition "owns" the failures of its own period in office: the debts, the deficits, the "captain's call" discretionary expenditures (including those of Turnbull) and the tendency to immediately spend any savings achieved. Those in Treasury and those imported to guide it, who believe in the virtues of low taxes, lower spending and zero debt, have no grounds based on performance for confidence in thinking that the Coalition is more trustworthy, reliable or stingy on the national accounts.

The Coalition's own inept policies and salesmanship failures were compounded by the appearance of being mean and unfair on social welfare programs, by clear breaches of promise, and by its ultimate abject surrender to criticism, unpopularity and a problem Senate in the second Hockey budget. Artless salesmanship by Joe Hockey, Christopher Pyne and Peter Dutton made the humiliation worse. By all accounts, the first Morrison budget will be as soft – and, like the second Hockey one, deliberately "boring".

Whether a budget is "soft or hard", "tough or weak" is not primarily a matter of what the times and circumstances demand. It is about whether programs, policies and proposals can be retrofitted into previously announced declarations about the fiscal virtue to be employed. Only a major external force, such as a GST, will usually explain a failure to live up to promises. The Turnbull expenditure review committee has, stupidly, declared that it will not entertain new policy or program proposals this year. It seems that Turnbull does not plan to go to the election seeking a mandate for some substantial change.

Even now, Turnbull has some street cred on economic matters, if only because he made a personal fortune in the marketplace. But that cred has not transferred to the government generally. Least of all to his hapless Treasurer, Scott Morrison, who looks increasingly out of his depth. Either he, or Turnbull, or perhaps the whole cabinet, have proven less than inventive in devising new policy. Heaven knows what the Treasury is telling him, how it is scripting him, or whether he can follow, or understand, the script. But he has looked uncertain, inconsistent and far from confident or sure. He's been a well-regarded minister, strategist, tactician and salesman. Some of that should have been invested in the struggle. He is, at the moment, having to be carried by others, particularly the prime minister. If all that the budget offers is some tightening of existing programs, the chances are that they will be causing political drag during the election campaign.

The public may have already seen the best of Turnbull. He is very popular, but, it seems, very cautious about doing anything to leave a lasting mark on things. He shouldn't leave it too long to put his money on the table. The odds are shortening.