It’s a climate change election but the political party with the utmost ambition on climate – yes, the Greens – is somehow on the outer. Flagging in the polls, cold-shouldered by Labor, the Greens have spent the campaign jostling elbows with a bunch of high-profile independents in the inner cities and battling the alt-right in the Senate.

Greens leader Richard Di Natale gave a rousing speech to the National Press Club on Thursday, pumped after an Easter family road trip from Melbourne to Brisbane with his predecessor Bob Brown’s Stop Adani convoy which will finish in Canberra on Sunday. Di Natale rattled off a list of impressive achievements in his first full term as leader of the Australian Greens, including paving the way on marriage equality, the banking and disability royal commissions, Medevac laws and a national anti-corruption body. Electorally, however, there is little sign the Greens are about to reap the rewards of its “thought leadership” among the parties.

Newspoll has the Greens’ primary vote steady on 9%, where it has been since October, and for much of the decade. An Essential poll this week also showed support at 9%, down from 12% six months ago, notwithstanding a major shift in public sentiment on climate after another angry summer of record temperatures, wildfire, floods, and the unprecedented fish kills in the Darling River.

Former Greens leader Christine Milne says climate is on the agenda in a way it has not been since the 2010 election, which marked a record high for the party, and she expects voters will start backing “people who are gutsy on the environment and not equivocating … the Greens are out there in the spirit of bold policy and the times call for bold politics”.

Take the school strikers marching on Friday, for example. The Greens are the only party that can tick off on their three key demands: 100% renewables by 2030, no new fossil fuels, and “Stop Adani, stop stop Adani”. The party’s election platform, launched on Thursday, does not go all the way – there is no climate emergency declaration, for example, as is being pushed by UK Labour leader Jeremy Corbyn – but it does represent decades of hard-yards policy, and does put a price on carbon. Di Natale got his loudest applause when he linked progress to donations reform, hinting at the vested interests behind Australia’s major party failure on climate: “we have no hope of cleaning up our environment until we clean up politics.”

Christine Milne, shown with Richard Di Natale and Bob Brown in 2016, is heartened by the Greens’ performance in NSW. Photograph: Julian Smith/AAP

Before the Greens clean up politics, however, they need to clean up their own act. A reckoning looms for the party in a fortnight’s time, after an election in which the party is fighting to hang on to six of its nine Senate seats – one in each state – and retain its sole lower house seat of Melbourne, held by Adam Bandt. Unless it pulls off an upset in one of a few prospective electorates, the best the party can hope for is to to hang on, and there is a real prospect of going backwards.

In an half-Senate election, as ABC election analyst Antony Green pointed out this week, historically only one crossbencher gets elected per state and in this election the six Greens are slugging it out with six other sitting crossbenchers. Victoria, Western Australia and Tasmania are considered relatively safe for the Greens, while New South Wales, Queensland and South Australia are harder.

Compounding the difficulty, historically the Greens vote has suffered in state and federal elections when the Coalition has been in power and a swing is on, and progressive voters worry their vote will be wasted. “That is something that we’ve had to battle with over the years,” says Milne. “When people want a change of government away from the Coalition and to Labor, they don’t understand the voting system well enough to know that they can actually have both, that they can vote for a Green and still get a change of government.”

If the Greens vote is down on 18 May, there will surely be a rethink of the party’s direction under Di Natale, who committed on Thursday to carrying on as leader, whether the result was good or bad. South Australian senator Sarah Hanson-Young, who had previously run as deputy, has already ruled out any challenge after the election, when party rules dictate an automatic spill of leadership.

Sarah Hanson-Young has ruled out any challenge to the Greens’ leadership after the election. Photograph: Roy Vandervegt/AAP

Clouding Di Natale’s leadership is the continuing fallout from the disastrous campaign in November’s state election in Victoria – his home turf and power base – and the tumult in NSW which resulted in the resignation of Greens MP Jeremy Buckingham. The party is keeping a tight lid on things two weeks out, but the pressure is building for a fix to a culture that in some state branches has turned toxic, hurting membership and morale.

Di Natale will not be drawn on the party’s internal brawling, which he does not believe is worse in the Greens than in the other major parties and is generally harder to keep a lid on nowadays. “One of the big changes in politics,” he says, “is that so many conversations between people are now public conversations because they are prosecuted online and reported in the mainstream media”.

One person willing to speak up is social worker Alex Bhathal, former longtime candidate for the inner Melbourne seat of Batman, who resigned from the party in January, and is now calling for change starting at the top. Bhathal tells Guardian Australia there has been “a failure of leadership at the federal level of the party, a failure of vision and of capacity; a strategic failure”.

“There’s a lot of woolly thinking in the party,” says Bhathal, “sanctimonious thinking by people who have an incredible sense of entitlement and a lot of privilege in their lives”.

Bhathal fell victim to a bitter smear campaign from within her own party, which erupted during the byelection last year in Batman (since renamed Cooper), which she believes was grievously mishandled by the party leadership. Ultimately the prize seat was handed on a plate to former president of the Australian Council of Trade Unions Ged Kearney, who is expected to keep it. That historic stuff-up has had cascading consequences, feeding into the ensuing state election result, in which the party lost five of its eight MPs – four in the upper house plus the state’s first Aboriginal woman MP, Lidia Thorpe, in the Northcote electorate. Many of Bhathal’s supporters have quit, state membership is down by a third, and donors have also been dropping off.

A confidential review of the disastrous Victorian campaign, seen by Guardian Australia, deferred big decisions on reform until after the federal election. After the ABC and the Age reported on the review at the end of March, former MPs Samantha Dunn and Nina Springle quit the party, protesting against the lack of action. Springle, who was deputy for a year to state leader Samantha Ratnam, says there has been no accountability for the result: “It’s bizarre, I’ve never seen anything like that before.”

Alex Bhathal (right) says there has been a failure of leadership at the federal level of the Greens party. Photograph: Alex Murray/AAP

“Losing more than half your party room is not a success by anyone’s measure,” Springle wrote in her resignation letter. “If it happened in any other party it would be considered a wipe-out. There appears to have been little if any critical self-reflection … the party establishment continues to stumble from one train wreck decision to the next, leaving a wake of destruction behind it, blatantly disregarding the human toll, all in the name of something I cannot even name anymore.”

The party’s cratered support in Melbourne’s inner north also partly explains the Greens’ strategic shift in this federal election to the other side of the Yarra, to concentrate on the upmarket Liberal-held seats of Kooyong, being contested by recently-recruited human rights lawyer Julian Burnside, and Higgins, where former VFA footballer Jason Ball is on his second attempt.

Di Natale hopes the small-l Liberal voters disappointed at the toppling of Malcolm Turnbull will switch to the Greens, although this may be making a virtue of necessity. The strongest prospect is another Labor -held seat in Melbourne’s inner south, Macnamara, where Michael Danby is retiring and the Liberal candidate Kate Ashmor has proved a liability, once comparing Chloe Shorten to a pig. The Greens’ Steph Hodgins-May almost won the seat in 2016, and a preference deal has been done with Labor that could help her to an against the odds victory this time. Elsewhere, it’s slim pickings: in Melbourne, Liberal and Labor have again ganged up in a preference deal at the expense ofthe Greens’ Adam Bandt. He remains the clear favourite to hang on.

Bhathal points to the party’s leaders at state and federal level: “Sam and Richard make what look like major tactical mistakes in terms of the long-term interests and prospects of the Greens because they’re primarily concerned about preserving their power base within the party. They are insular leaders with no interest in building the party as a mass political movement because that would erode their ability to control the party.” She has given up on the party, saying “it’s not going to be the movement we hoped it would be”. Her hope is that Bandt will emerge as a future leader: “I think he’s the only person who can make the party matter again.”

A key finding of the Victorian election review was that the Greens are getting better at winning lower house seats, and less effective in winning upper house ones, and should be holding “a discussion as a party regarding what this means for our long term trajectory”. The same trend may be playing out in the current federal campaign: on the ground, a well-placed source says support for the Greens in Melbourne’s suburbs has been “gutted” after the state election and the party is struggling to field candidates and source volunteers, including at crucial pre-poll booths, many of which are unmanned, with dire implications for the Senate vote. “I don’t know what they expected when they lost all their suburban MPs,” the source says. “The reality is, each level of government feeds into the next. That’s what always differentiated the Greens from the Democrats – our strong local and state government presence. When you lose five of your state MPs, four of them covering Melbourne metro, that’s got to have an impact on the Senate vote.”

In the recent Victorian and NSW elections, the Greens statewide vote dropped in both houses, although there have been swings towards the party in certain inner-city lower-house seats. In the NSW poll in March, the Greens held their three seats in the legislative assembly – Newtown, Balmain and Ballina on the north coast – and both upper house seats, notwithstanding that the party went perilously close to splitting over the handling of unproved sexual harassment allegations against Buckingham, who quit in December. His ally, upper house MP Justin Field, defected from the party soon after the election and former MP Dawn Walker resigned her membership last week.

Milne was surprised and somewhat heartened at how well the Greens did in NSW, and says the result augurs well for the federal election. “Usually that level of division is ‘death’ in terms of electoral politics,” she says. “I’m pleased that the sitting MPs were returned but I’m disappointed the upper house didn’t carry as well as it might have and should have. That really points to the view, that I’ve expressed before, that for the Greens to be a party of government they have to have broad appeal, and not just to the inner city, and that means that concentrating on the Senate and the upper house in state elections is important as well as inner-city seats.”

The Greens’ road to government always went via the balance of power and an eventual coalition with Labor, including ministries, as has occurred in Tasmania and the ACT. But Labor leader Bill Shorten this week dismissed Di Natale’s offer to work together on climate policy in the next parliament, accusing him of a search for relevance, and both sides have sworn off entering into any formal alliance. So the two parties remain on a collision course, permanently, and a Greens government at a federal level seems as far away as ever.

The lawyer Sue Higginson, who ran the NSW Environment Defenders Office for 15 years, and went close to winning in the northern rivers seat of Lismore, believes the Greens are the fix for a corrupted political system and the climate crisis. “Let’s face it the largest problem we’ve got is the two-party system,” she says. “The major corporate donors to the two-party system don’t see the difference – they’re happy to work with either and it’s one of the biggest factors causing the inaction on environmental issues, particularly climate change. The Greens are the only political party that doesn’t take those corporate donations, [and they] are more relevant now than ever.”

On Thursday, Di Natale pointed to the encouraging NSW election result, observing that the party had been “written off” beforehand, as always. In a recent interview with Guardian Australia, he complained that the media were fixated on the Greens’ internal feuds, and were failing to cover the party’s positive achievements. “We expect that treatment from News Ltd,” he said, “but some of the more reasonable outlets seem to criticise the Greens just to show they’re balanced, which of course is itself a form of bias”.

In Melbourne, the Liberals and Labor have again ganged up to recommend each other over the Greens’ Adam Bandt, who is a clear favourite to hang on. Photograph: Mike Bowers/The Guardian

Milne blames fossil-fuel industry donations bolstering the major parties for the Greens’ flatlining polls, and Rupert Murdoch’s News Corp papers and Sky, which are talking up Clive Palmer as kingmaker on an almost daily basis. “Murdoch has a lot to answer for in Australia,” says Milne, “and there is a growing awareness of the extent to which [he] distorts our democracy”.

Nonetheless, she is confident in the party’s prospects come election day, and has strongly backed Di Natale’s leadership. She believes the Greens will retain Melbourne, has a chance in the other fancied lower house seats – and may be in for an upset win in the new seat of Canberra. She says she can see a path to victory in the three toughest Senate contests. In South Australia, “I think Xenophon dropping out and his party not being so prominent is a positive thing for Sarah”. In Queensland, the demise of group voting tickets will count against the profusion of far-right candidates who will be unable to swap preferences. “They will all split the vote,” says Milne, predicting Larissa Waters will get over the line helped by concerns about Adani and the Great Barrier Reef. In NSW, Mehreen Faruqi, the first Muslim woman in the Senate, has taken on a high profile in recent debates on hate speech, particularly following the Christchurch massacre, and is expected to hang on. “I think Mehreen is a very good candidate for us; she’s got reach into Western Sydney in a way that the party hasn’t had until she got elected in NSW, she’s been an outspoken advocate on education in particular. I think they’re all likely to be returned.”

Paddy Manning is the author of Inside the Greens: The True Story of the Party, the Politics and the People, to be published by Black Inc in August