As the pressure builds on Kevin Rudd before Monday’s leadership showdown, the Gillard camp will be scratching around to produce a “smoking gun” to definitively paint the former foreign minister as a manipulative Judas. But the hard evidence directly fingering a personal Rudd campaign has so far proven seriously elusive.

Either Julia Gillard is struggling to produce the killer blow or she is saving up the dirtiest dirt for maximum impact in the Sunday tabloids.

Last night on 7:30, Heather Ewart claimed that right-wing Melbourne Ports MP Michael Danby told her that “four” journalists — two ABC reporters and one News Limited (the affiliation of the fourth was unclear) — had been placed on the Rudd drip. Ewart said Danby had told her their identity off camera. (Danby’s office didn’t return Crikey‘s calls this morning).

Multiple Press Gallery sources named (and the record shows) that Peter Hartcher, Phil Coorey, Dennis Shanahan and Laurie Oakes have been regular targets of Rudd leaks — a list that doesn’t exactly tally with Danby’s breakdown. The reference to two “ABC journalists” would seem to rule out Chris Uhlmann, given he was conducting the interview, Ewart, who was reporting the story, and Ewart’s husband Barrie Cassidy, given torrents of bad blood that continue to wash between him and Rudd.

The scuttlebutt was immediately mocked by Doug Cameron, who suggested Gillard loyalists had plied their cipher with bung information — how else would an out-of-the-loop third party such as Danby even know about it?

That follows Cassidy’s extraordinary pronouncement on The Drum last week that he knew “the names of some of those he [Rudd] has spoken to” about Rudd’s two-stage strategy to seize the leadership:

“I know where he said it — in his office — on a parliamentary sitting day — and I know what he said. He told them a challenge would happen; he told them he was prepared to lose the first ballot and go to the backbench; and in one conversation he laughed about the prospect of Gillard stumbling again.”

Cassidy’s stoushes with Rudd date to 2007, when Sam Maiden, then with The Australian, penned an amusing story headlined “Cassidy declares war on Rudd”, using quotes that Cassidy later wrote were in fact made by an Aunty colleague.

Six days before the election, Rudd declined to appear on Insiders, sending Gillard in his stead. This apparent treachery prompted an on-air outburst from Cassidy, who complained that Rudd preferred the “vaudeville” of Rove to his serious Sunday morning political stylings.

There’s no doubt Rudd has been active in corralling the gallery, putting Bruce Hawker on late-night texting duty to get the message out. More significantly, insiders agree that Rudd’s relations with Chris Mitchell and The Australian have regained the levels of bonhomie reached when Rudd was anointed as his son’s godfather, recovering from the lows of the 2008 “what’s the G20?” debacle.

And Maiden, of course, has since splashed with her share of Rudd leadership exclusives, including a crucial front page on the final day of December’s ALP conference that kept the issue kicking along nicely.

Asked this morning whether she had ever leaked against Rudd while he was PM, Gillard implored the Adelaide press pack to call their Canberra colleagues and tell her that she had absolved them of their journalistic obligations to protect sources.

“To a person they would say no because I never did,” Gillard said, an amusing claim given her office’s multiple current and former staff members who were doing (and continue to do) just that.

Therese Rein also picked up the theme at a heartfelt Brisbane doorstop, complaining about the “negative backgrounding and undermining” of her beau, “that’s just gone on and on”.

Meanwhile, Stephen Conroy regurgitated Wayne Swan’s and Tony Burke’s overnight explosions, highlighting the foreign minister’s “constant leaking and destabilisation” campaign since his knifing in 2010, without producing any specifics.

But with four newspapers to go before Monday, the quest for the golden hatchet — on both sides — can’t be far from bearing fruit.