Prime Minister Julia Gillard during question time at Parliament House on Tuesday 12 February 2013 Photo: Andrew Meares

Kevin Rudd looked quite at home in Parliament during question time recently. Photo: Andrew Meares

THE fight over the Labor leadership is shaping as a battle of attrition, with a key backer of Kevin Rudd saying there is no deadline for a change of leader and that it could happen at any time up to and including the formal election campaign.

The source cites the precedent set by Bob Hawke in 1983, when he took the Labor leadership from Bill Hayden on the same day that Liberal prime minister Malcolm Fraser called the general election. Mr Hawke went on to lead Labor to a 25-seat victory.

The open-ended strategy contrasts with comments made by Rudd supporters before his challenge in February last year that he would need time in the job to re-establish his authority.

It also contrasts with reports early last week, following Julia Gillard's disastrous showing in the Nielsen poll published in Fairfax papers on Monday, quoting Rudd supporters saying that a challenge could come as early as mid-March.

But not all Rudd backers embrace the possibility of a challenge in the second half of the year, with one telling Fairfax Media that he doubted Mr Rudd would be interested in being drafted so close to a poll.

The open-ended timetable is based on a belief that leadership change will become inevitable as the election approaches if the Prime Minister's standing in the opinion polls remains parlous. It is suggested caucus members would put aside any personal reservations about the former prime minister if they believed he could deliver a better outcome for the party.

Some Rudd supporters believe he is already so well known to voters that he would not need the period usually required for a new leader to consolidate their authority, profile and popularity before an election.

One source suggested a change closer to polling day might even prove advantageous, giving the opposition less time to tarnish Mr Rudd's image. It could also serve to preserve the leadership of Tony Abbott, with many Labor MPs considering him a less formidable opponent than Malcolm Turnbull.

However, talk of a late challenge also contains a tacit admission that Mr Rudd remains well short of having the support to topple Ms Gillard any time soon, and that any change of leadership can only occur if Ms Gillard continues to flounder in the opinion polls.

Such a strategy, if successful, could potentially pave the way for a less acrimonious handover of power compared with an earlier, knock down, drag out challenge.

It does, however, require Mr Rudd to maintain a high public profile to keep his approval ratings high in opinion polls. Mr Rudd's media appearances have intensified this year and come as a constant irritant to, and distraction from, the Prime Minister's own election strategy.

The Nielsen poll published by Fairfax last Monday indicated 61 per cent of voters preferred Mr Rudd as prime minister, compared with 35 per cent who favoured Ms Gillard, the gap between them widening 8 points since December. Ms Gillard's net approval rating plummeted to minus 16.

With polling guaranteed to play a critical role in shaping politics in the lead up to the election, it is understood both pro and anti-Rudd forces are regularly polling marginal seats.

The next public shot in the polling war is likely to come as early as this week, with the publication of a Newspoll expected on Tuesday.