The most significant question in tomorrow’s leadership ballot is the margin of Julia Gillard’s expected victory. On that bears whether Kevin Rudd will be the next Prime Minister or a third contender, later in the year.

A substantial showing for Kevin Rudd, in the high thirties for example, would leave him as the clear candidate for when Labor MPs, or perhaps her own backers, moved to force the Prime Minister out later in the year. Rudd can sit on the backbench, completely silent, doing nothing but writing letters to his constituents, and it will be an ever-greater contrast with the mess that is Julia Gillard’s Prime Ministership.

A poor result for Rudd would humiliate him and leave him badly damaged — repudiated by his own party despite his insurgent-like appeal to the electorate. It would open the way for a third party contender — Stephen Smith, Bill Shorten or Simon Crean appear to be the most likely MPs — to become the sanctioned replacement for Gillard, who may well be tapped on the shoulder by the same powerbrokers that installed her. Rudd might contest again at that point, but he’ll be doing so with a poor base of support, while the Gillard camp and undecideds will lock in behind a Gillard successor.

A result in between will leave the situation more fluid, and much less clear for Labor, and more damaging. Labor needs a clear result either way. Every extra vote strengthens Rudd’s long-term hand as the replacement for Gillard. But the contest has come on too early for him; ideally, waiting until after the Queensland election, and further missteps from Gillard, would have accelerated the drift of MPs to him. The contest coming on in February is therefore a boon to the Gillard camp – not merely is she likely to easily defeat Rudd, but it gives party powerbrokers time to think about a long-term replacement of the “anyone but Kevin” variety.

The only guarantee is that Gillard won’t be Prime Minister by the end of the year. If it were merely a question of her poor polling as a result of hard decisions and, as Wayne Swan claims, constant destabilisation by Rudd, she would have plenty of time to turn things around against Tony Abbott. But that’s not Labor’s problem, or not its only problem. Gillard has lost the trust of voters, fail to convey to them what she really stands for, and has, along with her advisers, poor judgment. She has the time to turn it around, but not the skills or goodwill in the electorate.

Which means the only real question is, who will replace her later in the year — Kevin, or anyone-but-Kevin? That’s the important result tomorrow morning.