At the pointy end of the political year, Malcolm Turnbull is a weakened leader under siege from within and without.

The High Court has thrown his one-seat majority Government into disarray at a time when he was hoping for clear air to get on with policies that might help shore up his disastrous polling — things such as tax reform, infrastructure and housing.

Four Corners spoke to conservative activists about their frustrations with Mr Turnbull's leadership, and former Liberal leaders John Hewson and Jeff Kennett also pass their judgement. Their conclusions are harsh.

Turnbull's inconsistency

The citizenship question has threatened the Government's future. Dr Hewson tells the program Mr Turnbull has failed to deliver outcomes, instead delivering an impression of an inability to manage issues as they've arisen.

"You would have thought that when the issue broke, he [Mr Turnbull] should have [had] a complete check of all the members of Parliament to say, 'Have we got an issue?'" Dr Hewson said.

He says there's been an inconstancy in Turnbull's approach that has destabilised his leadership.

Once again, the public see politicians playing with the semantics. It's no surprise they don't like it.

"On the one hand, you accept [Matt] Canavan standing down but you protect [Barnaby] Joyce and [Fiona] Nash … on a punt that you can second guess the High Court," Dr Hewson said.

"There's an issue management there that's just been let run and mismanaged."

Malcolm Turnbull is without a Deputy PM, with Barnaby Joyce on the campaign trail in Tamworth after being ruled ineligible to be an MP by the High Court. ( AAP: Perry Duffin )

This week, we'll see the election of a new Senate president following Stephen Parry's tardy recognition of his own citizenship problems. Mr Turnbull's idea of a broad citizenship register is likely to throw up more uncertainty.

A series of by-elections is now likely and there's even talk of an early general election. It all adds to a perception of chaos around the Government.

What it means to be Liberal

This week will also see the result of the postal ballot on same-sex marriage. Polls suggest there will be success for the Yes case but again no-one's entirely certain and the whole thing has emboldened and energised Mr Turnbull's critics on the right of the party.

Now, 72 years on from Robert Menzies' foundation of the party, the fights about what it means to be a Liberal and who the party represents have become more defined than ever around these cultural and social issues.

Tony Abbott has used same-sex marriage and the energy debate to connect with the conservative Liberal Party base. ( ABC News: Matt Roberts )

Tony Abbot has been relentless in his use of this issue and the energy debate to stir up a Liberal Party base that is far more conservative than the current leadership.

Mr Kennett, for one, says Mr Turnbull has been far too tolerant of those on his own side who won't play as part of the team.

"He's paying the price for that tolerance, but at some stage even he must realise … that this sort of division is unacceptable."

Mr Kennett says those who don't want to be part of the team should leave the party or the members should throw them out. However the membership of the party is now far more conservative than the leadership and there are real threats emerging that a good deal of them may well leave the party — particularly in NSW.

Abbott's conservative challenge

The so-called reform movement in NSW — led by forces on the right aligned to Mr Abbott — put forward a motion to give every party member a vote in every preselection. This is a direct challenge to the dominance of Malcolm Turnbull's allies in the moderate faction in the state and, if successful, will overturn provisions that were put in place more than a decade ago to prevent branch stacking.

The so-called "Warringah motion" was passed at an extraordinary party meeting in July but still needs to be ratified by 60 per cent of a meeting of the NSW state council on December 9. The moderates control the numbers at state council and will put forward an alternative motion — a compromise the right say they won't accept.

"It will not be business as usual": Former Liberal John Ruddick. ( ABC News: Four Corners )

One of the conservative activists behind the push in NSW is former Liberal John Ruddick. He tells tonight's Four Corners he has a database of 10,000 members and former party members and he'll use it to split the party.

"If [the motion] doesn't get up, we'll call a meeting, probably for Sydney Town Hall," Mr Ruddick said.

"We'll invite 10,000 people. We'll probably invite Cory Bernardi along as a guest speaker and we'll have a big discussion about what we're going to do. But it will not be business as usual."

Cory Bernardi has also used the same-sex marriage campaign in his messaging. ( ABC News: Matt Roberts )

Senator Bernardi has also used the No case to build support for his new conservative party and his message is resonating.

"I've given up trying to convince people not to join Cory Bernardi because they might be right," Mr Ruddick said.

"We might all be joining him, you know, if things don't go well."

Victoria's 'hostile takeover'

In Victoria, the conservative insurgency has been underway now for the past three years, led by a young ambitious activist, Marcus Bastiaan, who has support from Victorian party president Michael Kroger.

Marcus Bastiaan led a drive to sign up social conservatives to branches of the Victorian Liberal Party. ( ABC News: Four Corners )

Mr Bastiaan has been running a seat-by-seat campaign signing up social conservatives from church groups, Mormons and diverse ethnic communities.

The campaign has paid off and the Bastiaan/Kroger group now have effective control of the Victorian party's administrative committee, which determines the timing of preselections.

The move has been described as a hostile takeover by some but Mr Bastiaan tells Four Corners those people who, "don't like a big Liberal party perhaps should go and join another party".

A 'broad church' divided

The Liberal "broad church" is more divided than ever and Mr Turnbull's leadership is now more tenuous than it's ever been.

He came to the leadership promising to do things differently: a reaction against the slogans and rigidity of an increasingly unpopular Abbott government. But Dr Hewson says he's failed to live up to the expectations he created.

"He's probably had one of the fastest falls in personal standing in our history in terms of how fast he went from all options on the table to no options on the table," he told Four Corners.

"And worse still, no outcomes that really matter to the average voter."

For Mr Turnbull, there are a torrid few weeks ahead.

Getting to Christmas will be tough for a prime minister now in a weak position on so many fronts.

Activist social conservatives in his own ranks will continue to take advantage of his weakness and undermine his leadership.

A strong showing in the coming Queensland state election for One Nation would erode his authority further.

Rebuilding enough public support from here to win an election will be an enormous challenge.

Holding the Liberal Party together under his leadership will be another.

Malcolm in a Muddle airs on Four Corners tonight at 8.30 on ABC1.