The size of the win or loss by Malcolm Turnbull and Bill Shorten will determine how secure they are in their positions and shape the Australian political landscape for the next 12 months and beyond. 
For Turnbull, a win that reduces the Coalition's House of Representatives majority to a single figure will diminish his authority and increase the prospect of internal tensions, outbreaks of ill-discipline and even insurrection.
Such an outcome would suggest the industrial legislation that was the trigger for this double dissolution will struggle to pass at the joint sitting that will follow - a humiliating rebuff to the returned prime minister.
With the prospect of an even bigger and more unwieldy crossbench in the Senate under the voting reforms Turnbull championed, a narrow win would also offer no guarantee that the company tax cuts that are the centrepiece of the Coalition's campaign will be legislated.
For Shorten, a net gain of fewer than 10 seats will dramatically increase the prospects of a leadership challenge from the man who decisively won Labor's popular vote after the last election, Anthony Albanese.
It would also invite the conclusion that Labor erred in committing itself to higher budget deficits than the Coalition over the next Parliament and over-reached with its Medicare scare campaign.
The old maxim is that a win is a win, but it will not apply to Turnbull if the margin is wafer thin - just as it did not apply to Julia Gillard in 2010.
In her case, she negotiated an agreement to govern from a hung parliament, but her precarious position left her vulnerable to destabilisation on behalf of the man she tore down: Kevin Rudd.
The truth is that Turnbull saved the Coalition from a crushing defeat if Abbott had remained leader, but this will not be the test of his colleagues, especially those who remain loyal to the man who brought the Coalition back to power so emphatically in 2013.
In their view Turnbull has run on the policies and agenda of the man he replaced, but without Abbott's ability to exploit the fear factor.
If Turnbull is returned with modest majority, the task of managing his own side and the Senate crossbench may prove beyond him.
There is no obvious comparison for the situation that confronts Shorten, who could halve Turnbull's majority yet still face rejection by the party he has led, by almost any measure, with distinction. His budget reply of 2014 crystalised the community sentiment that Tony Abbott had broken solemn commitments and introduced measures that were unfair, though in the end Abbott was the agent of his own demise. It has been in his response to the Turnbull ascension that Shorten has emerged as an alternative prime minister, presiding over the release of a comprehensive suite of policies and communicating with more clarity and verve.
In my view, he has done more than enough to earn the support of his caucus and party membership for a second crack in three years if he falls short.
Both leaders can be satisfied with their campaigns, despite the Coalition's lack of willingness to engage in debate on issues such as climate change, workplace relations, higher education and Indigenous affairs. During eight relentless weeks, neither made a major mistake.
If the contest was short on excitement and inspiration, and it was, it was conducted with civility and mutual respect. For that we can be thankful.