Bronwyn Bishop’s remarkable attack on Malcolm Turnbull this week showed she was worried about retaining preselection in her seat of Mackeller, according to local Liberal sources, and not just because she has been singled out by party donors as deadwood.

Local sources point out that, while Bishop and her supporters have a solid grip on smaller branches in the electorate, centred on Sydney’s Pittwater and Northern Beaches, her hold on larger branches has slipped and she may have to rely on support from the party’s Right-controlled State executive to overcome the loss of support in the branch component of the preselection vote.

Bishop, a relic of not the Howard years but the pre-Howard years, lashed out at Turnbull after leaked correspondence from a large corporate donor identified her among the non-performing MPs that needed to be cleaned out in the cause of party renewal.

Bishop’s status as deadwood is unimpeachable, and probably has been since her disastrous move to the House of Representatives led to a swing against her in 1994. In recent years she has tried to re-cast herself as some sort of guardian of Chamber practice. She had a failed tilt at the Speaker’s chair after the 2004 election and these days her main contribution to public life is to rise during Question Time clutching a copy of the Standing Orders, try to look like a barrister by peering over her glasses and raise points of order that are frequently wrong.

The two most likely challenges, sources say, are Jim Longley and John Brogden. Longley, a former member for Pittwater and minister in the Fahey Government, is now a senior Commonwealth Bank executive and is said to have threatened to enter previous preselections, but never followed through (Longley did not return calls before deadline).

John Brogden’s political career was thought to be over after his departure from the State Liberal leadership and subsequent mental health problems. He again ruled out a return to politics in December after leaving his position as CEO of Manchester Unity following a takeover by HCF. Brogden followed Longley as Member for Pittwater.

Another Liberal figure often mentioned in Pittwater and Mackellar speculation, Jason Falinski, ruled himself out when contacted by Crikey. Falinksi, a former Young Liberal President, Australian Republican Movement spokesman and chief spear-carrier for Malcolm Turnbull in the latter’s successful tilt in Wentworth, is now an independent local councillor on Warringah Shire Council and is no friend of Bishop’s. Falinksi was responsible for an hilarious Notice of Motion in February that called for pictures of the Queen be put up in Council Chambers because there was considerable confusion among monarchists as to who our head of state was. The motion, which is said to have infuriated Bishop, was successful.

Liberal sources point out that successful preselection challenges in NSW are the exception rather than the rule, especially given the cost of legal fees when preselection stoushes end up in court. Unlike Labor, they say, the party has no structure for dealing with the issue of renewal. Nevertheless, this time around Bishop’s preselection is likely to be a lot more competitive. Her overreaction this week shows how nervous she is.