Having helped destroy a Coalition government, Barnaby Joyce now threatens to inflict immense damage on the Coalition — if there is to be one — in opposition.

In a profession riddled with giant egos and hypertrophied self-importance, Barnaby Joyce still stands out as Australia’s most selfish politician. At no stage have his numerous personal and political failures punctured his conviction that whatever Barnaby wants, Barnaby should get. And it doesn’t matter what the cost is to anyone else — his family, his colleagues, the national interest.

It’s a view that is a refinement of the basic Nationals ethos, that politics is about taking as much as possible from the nation without regard to anyone else.

Joyce leads a party that garnered just 4% of the national vote in the House of Representatives, along with a portion of the 7.7% of the LNP vote in Queensland. That is, he represents well under 10% of Australian voters — far fewer than the Greens, who secured nearly 12% of the vote nationally. The LNP vote fell by more than 4%. The Nationals’ overall vote fell by 0.3%. The only state where it rose was in Victoria — by 0.3%.

Can Joyce claim credit for that? Joyce only deigned to grace Victoria with his presence for a few hours in total in recent weeks, flying in and out just three times over the course of a six-week campaign. He didn’t dare go near the electorate of Gippsland, home of Darren Chester. Chester’s decency and commitment to the public interest are evidently unfathomable to Joyce, given he forced Chester out of the ministry when he returned to soiling the role of deputy prime minister last year. Chester got a 4.4% swing to him.

Joyce instead devoted considerable time to campaigning in the Northern Territory and the Hunter Valley. How’s that working out? The Country Liberals suffered an 8% swing in the NT and Labor held both its seats. Labor got a swing to it in Hunter. The “best retail politician in the country” lowered the vote where he campaigned, whereas it increased in seats he stayed clear of.

That as nothing, though, compared to his role in lowering the Liberal vote. Scott Morrison might have evoked visceral hatred among voters — especially women, who were waiting for him with baseball bats — but Joyce, along with Peter Dutton, formed a triumvirate of electoral toxicity with Morrison that it’s hard to recall the likes of.

Joyce provided a convenient, one-size-fits-all, all-you-can-eat symbol of what was wrong with climate policy, integrity, and the basic standards of decency in public life. Not for nothing did the teal independents make liberal — pun intended — use of the phrase “A vote for X is a vote for Barnaby”.

Surveying the smoking ruins of the Morrison government, Joyce — true to form — doesn’t care, saying it’s not his problem, comparing his influence to Tim Wilson losing Nationals votes in their seats, and flagging, inevitably, that net zero is again up for discussion.

Remember all those press gallery journalists who devoted acres of columns to explaining that Morrison’s net zero strategy was a piece of political genius and a major triumph that would end the climate wars? What staggeringly insightful analysis that proved to be — senior political journalists queueing up to tell us a turd wrapped in a ribbon was the merriest of Christmas gifts. It was always a meaningless target with a meaningless plan. Turns out the bribes and pork-barrelling that Joyce exacted as the price for his grunted, tired endorsement of net zero are meaningless now too.

We know Barnaby is innumerate — he once claimed Australia was at risk of defaulting when its net debt was $50 billion, compared to $700 billion now. But clearly that innumeracy extends to the process of forming government. The Nationals remain a rump of reactionary bystanders without the Liberals. They can’t conduct their rorting and thievery without the Liberals. Making the Liberals unelectable, even by the Nationals’ own standards of political conduct, is profoundly self-defeating for them. But Joyce seems committed to inflicting as much damage on his Coalition partners in opposition as he did in government.

The path back to power for the Liberals will be infinitely harder with Joyce than without. If the Nationals won’t do the honourable thing and dispatch him to the backbench — or preferably out of public life altogether — the Liberals, for self-preservation, need to abandon the Nationals until they come to their senses. Barnaby Joyce isn’t just selfish, he’s profoundly toxic.