For the South Australia Greens parliamentary leader, Mark Parnell, one moment encapsulates the impact of Nick Xenophon’s return to state politics.

In an election campaign full of clashes between the state’s premier, Jay Weatherill, the Liberal leader, Steven Marshall, and Xenophon, a leaders’ debate on the environment last month offered Parnell the rare opportunity to share the spotlight.

When he flicked through the Adelaide Advertiser the next morning, Parnell tells Guardian Australia the local paper acknowledged the former environmental lawyer had “of course” won on his pet topic, but that was where coverage of him ended.

“What struck me was on this double page election spread, they’d cropped me out of all the photos, and had seven pictures of Nick,” he said. “I don’t want to be sour grapes, but that sums up how difficult it is.”

Rob Manwaring, a senior lecturer in politics at Flinders University, notes that the December Newspoll that sensationally pegged Xenophon as the clear preferred premier also saw support for the Greens shaved from 9% down to 6%. That’s enough to threaten the legislative council re-election campaign of the Greens MLC Tammy Franks, who Manwaring expects to fight it out with Robert Brokenshire of Cory Bernardi’s Australian Conservatives for the last spot left after SA-Best gobbles up the seats usually contested by the minor parties.

It is a familiar feeling for the Greens in SA, where they have always struggled to be the main protest vote outlet they represent in the rest of the country.

According to Parnell, the problem is a local soft spot for centrist parties – the state is the former heartland of the Democrats, who he remembers used to outpoll the Greens by 10 to one.

Now the oxygen is being consumed by the media-savvy Xenophon and his knack for making the papers with his visual gags and one-liners.

Manwaring thinks there is more to it than that, saying the Greens failed to capitalise on the decline of the Democrats and have struggled to compete with Xenophon because of unexciting campaigns and a lack of charisma among their ranks.

“Parnell is an extremely effective parliamentarian, but he perhaps hasn’t been so effervescent,” he said.

Tired of being sidelined, the Greens have had enough. In an act of political judo, their campaign launch turned the headline-grabbing power of Xenophon’s name against him, declaring themselves the only true no-pokies party by pledging to ban them outright, and blaming Xenophon for the continued presence of pokies since he first ran as the No-Pokies MP in 1997.

Parnell said Xenophon had become the “some pokies MP”, although he noted the gambling lobby had targeted SA-Best rather than the Greens.

“Perhaps they don’t consider us a real threat,” he laughed.

Greens preferences deals have put SA-Best below Labor in all seats bar one, and even behind the Liberals in several key seats, including Hartley, which Xenophon himself is contesting. It is a deal that could very well stop his election even if his party picks up seats in the upper and lower house.

Xenophon has questioned the Greens preference deal, pointing to his three-star environmental rating from the Australian Conservation Foundation compared with the Liberal party’s one-and-a-half stars and Labor’s two.

Franks defended the move by declaring that “blue Liberals and orange Liberals were exactly the same”, referencing the party colour of SA-Best.

Parnell echoed her position, noting Xenophon’s history of wind-farm scepticism, and adding that preference deals considered more than environmental policy.

He said Franks had advised him that Xenophon’s party did not return phone calls when the party determined preferences.

To Parnell, this reflects a broader sense of chaos within SA-Best, and he points to Xenophon’s history of being abandoned by politicians who join his team.

“It is not a grassroots movement with any kind of structure, whether in policy or administrative, everyone has to abide by what Nick wants,” he said.

“This experiment in personality-based populist politics, I don’t see them staying together as a cohesive unit. Nick’s got one shot at this, with all the mainstream media rooting for him.

“The Democrats are nowhere to be seen these days, but we’re still here, and we’re not going anywhere.”