If the polls and the experts are right, Malcolm Turnbull is poised to achieve a fairly comfortable victory, if, most probably, with a Senate likely to be as obstructive as the one it will replace. But he has done so at a serious cost. It is not only to his own credibility and authority in the party and the electorate, but, most likely to his place in history.

There always had to be an election this year. Turnbull became prime minister less than a year ago with a claim, almost certain to be vindicated tonight, that he could do better than Tony Abbott. But it has been closer than it has looked, and, for most of the campaign, his opponent, Bill Shorten has had the better of it. Even if Shorten proves the loser, it will hardly be because he was out-debated or outclassed: indeed, if both stay on after the election, there may be the most even contest between the two major parties in several decades.

The election saw Turnbull further diminish himself in the eyes of the electorate. It is doubtful he will ever retrieve the standing, or moral authority he once had. He has lost the halo of the statesman, and the coming man. No one will look to him for leadership. Success may see him last a long time, but he is now, irretrievably, only a politician. Naturally he is able but, like so many of the others (including Shorten) he is, apparently, not even one of firm convictions. He may prove to be, at best, the prime minister Andrew Peacock could have been had he had a real killer instinct.

The mystery was not why Turnbull seemed so wooden, and so bereft of anything much capable of inspiring his constituencies, other than from fear of a return to a Labor government, good or bad. It was why Turnbull channelled Abbott and Abbott themes throughout the campaign, at no stage inviting voters to adopt his own view of issues, or to endorse the leadership of his personality and predilections.

His resurrection 10 months ago reversed opinion polling predicting doom for the coalition, and revived business and consumer confidence. Over the succeeding months, his popularity ebbed away as he made only cosmetic changes to Abbott-era policies. His apologists figured that this had been, in effect, a condition of his acquiring the leadership. But they expected the real Malcolm would ultimately emerge. Turnbull approaching the electors in 2016 would be himself, no longer a political eunuch hostage to old bargains, they expected.

But a Malcolm Turnbull elected tonight, as he probably will be, has no leave from the electorate to move away from the social or fiscal policies of the Abbott government. Voters will not have given him a free hand, even in defining intrinsically vague ideas about economic and industry plans, job creation programs or means to bringing "stability" to our international relations in the wake of destabilising events such as Brexit, a President Trump, or some standoff between the US and China.

Still less has Turnbull leave or licence to deviate from the Abbott agenda on climate change, the human rights of boat people in overseas concentration camps, or the revival of the national broadband network as a fundamental infrastructure investment to empower the forthcoming national paradise of innovation, agility, resilience and a new economy. These were things he left to Labor. These are things he ruled out, just as he ruled out fiscal policies which might temporarily increase debt and deficits beyond that already forecast. Here's hoping for world revival if he is to prove as inflexible as he suggested.

Even an electorate which might have preferred to see the real Malcolm instead of a fiscal and social conservative behind a Turnbull mask will notice if he changes tack or direction in favour of policies he denounced during the campaign. They will not necessarily disapprove as such, but they will notice the hypocrisy and become even further confirmed in their cynicism about politicians.

More importantly, his many enemies in his own party can affirm, and with solid evidence, that he has had no popular endorsement for moving past the general social and fiscal policies promoted in the campaign. One could see some of those enemies (whether in his caucus or in the wider party organisation) tense and prepare for conflict whenever Turnbull was presented during the campaign with the opportunity to suggest that he would take a flexible approach to settled dogma. One saw them turn away, whether from relief or disappointment when, each time, he rejected the temptation.

Peta Credlin, now a detached observer of politics rather than an Abbott warrior, has predicted that the same-sex marriage plebiscite could cause a "very big schism inside the Liberal Party going back to territory of 2009, [when Turnbull was deposed, by Abbott]. Malcolm knows that very well because that's where he lost his leadership. I think it will also cause enormous stresses within the Coalition."

Turnbull is probably right in predicting that parliament will overwhelmingly endorse same-sex marriage if the electorate does at the plebiscite later this year. But he must fear that some of the party's social reactionaries, still indignant about the leadership of the party by a liberal, let alone Turnbull, will be spoiling for an opportunity for conflict with him over the issue. Best, for his personal and political peace, if he simply ignores their provocations.

Neither John Howard nor Tony Abbott allowed their internal enemies the same freedom of action to undermine or criticise government policy, even when it was made manifest by unilateral captain's decisions. Howard, for example, took some pleasure in having (one-time) party wets such as Philip Ruddock, Amanda Vanstone and Michael Wooldridge be the ones who had to do the tough "dry" yards, and to constantly reaffirm the ideological basis of the policies they were applying. And when Abbott set Turnbull a task of destroying the NBN, it was partly because he imagined that Turnbull would shrink from trying. Abbott, moreover, loved to set little fires by way of prosecuting the culture wars against his enemies, not least in moderate wings of his own party. Turnbull, instead, has proven completely gun-shy, at least since, in the first flush of victory, he rewarded his friends and deposed a few of his more tired enemies.

When Turnbull first began disappointing enthusiasts last year, those looking to excuse him would say that adhering to party decisions on same-sex marriage, or climate change, or bowing to moral panic in the party about transgender matters, was a part of the price he was having to pay to take over the leadership of a party that had become more conservative. All the more so given that the party was traumatised, terrified and deeply conscious of the disunity parallels with the Rudd-Gillard-Rudd years.

But his apologists believed that the "real" Malcolm – the progressive, tolerant and intellectual moderate would soon shine through; his personality and style would soon mark the style and approach of the party. And that it would become evident in the messages emanating from a new ministry, even if it contained conservatives.

As this failed to occur, some wondered when he had made a Faustian bargain of his soul for the appearance of power. His protests that the people knew him well, and that he has not changed, have been unconvincing.

If there is a real Turnbull, it seems that he has a personality entirely different from that he had before he entered politics, or from when he was the progressive leader of the opposition in 2009. It is true that his time in exile taught him something about listening, about consulting, and about being rude and brutal, as well as a fairly convincing serenity. But if he promised that he would behave differently, he did not threaten to have different broad ideas, ideals and approaches to public policy.

But he is now, it seems, convinced of the rightness of policies, for example on climate change, he once opposed. Or he has decided that there must be a difference between his personal views (for example on same sex marriage) and those he promotes from his position as prime minister.

If it is the latter, it could be called realism – an acceptance that the continuation of his leadership depends on his maintaining the general support of a fairly conservative caucus – unlikely, on average, to be any more moderate as a result of the election.

But it also invites the question of why he bothers. What it is about his conceit, his chairmanship or his fiscal wisdom that makes his expertise, as opposed to general character and judgment, the vital ingredient of government?

On several counts, it all puts me rather in mind of Robert Southey's 19th century poem, After Blenheim, a moral fable which I had to learn by heart at school. In the poem, children on a farm at Blenheim, in Bavaria, unearth a skull and ask their grandfather about it. He tells them he is constantly unearthing old skulls from the Battle of Blenheim, fought on the farm in 1704, more than a century before:

"Now tell us what 'twas all about, young Peterkin, he cries;

And little Wilhelmine looks up with wonder-waiting eyes;

"Now tell us all about the war, and what they fought each other for."

"It was the English," Kaspar cried, "who put the French to rout;

But what they fought each other for I could not well make out;

But everybody said," quoth he, "That 'twas a famous victory …

"They said it was a shocking sight after the field was won;

For many thousand bodies here lay rotting in the sun;

But things like that, you know, must be after a famous victory.

"Great praise the Duke of Marlbro' won, and our good Prince Eugene."

"Why, 'twas a very wicked thing!" said little Wilhelmine.

"Nay ... nay ... my little girl," quoth he, "It was a famous victory."

"And everybody praised the Duke who this great fight did win."

"But what good came of it at last?" quoth little Peterkin.

"Why, that I cannot tell," said he, "But 'twas a famous victory."

Another reason for recalling Southey was that he was, in his youth, a great radical, even, as the poem suggests, less than sound on national security problems. As he became older, his politics went sharply to the right.

The essayist William Hazlitt was rather scathing, in terms that mind remind some people of someone else: Southey "wooed Liberty as a youthful lover, but it was perhaps more as a mistress than a bride; and he has since wedded with an elderly and not very reputable lady, called Legitimacy."