Tony Abbott, who resoundingly won an election being “Dr No”, will bring all his formidable attack skills to trying to kill the push to change the definition of marriage.

In a pitch that sees him lined up against both his prime minister and his activist gay sister, Christine Forster, Abbott on Wednesday moved into the front ranks of the campaign resisting reform, ahead of the controversial postal ballot.

This brings back memories of 1999, when Abbott and Malcolm Turnbull were on opposite sides of another popular vote: the republic referendum. Just as then, so now, the Liberal Party goes into this vote deeply divided. This time the split is part of a wider internal schism.

Abbott had his lines rehearsed into a neat soundbite when he appeared on Wednesday.

“Obviously I’ll be voting no – but in the end this is not about the politicians, it’s about the people. It’s about your view.

"And I say to you, if you don’t like same-sex marriage, vote no. If you’re worried about religious freedom, and freedom of speech, vote no. If you don’t like political correctness, vote no – because voting no will help to stop political correctness in its tracks.”

Thus he tossed the battle around marriage equality into the centre of the culture wars.

As the Senate rejected a new attempt to legislate a compulsory plebiscite and the government defaulted to its fallback option, we got a taste of the campaign that will accompany the voluntary postal ballot, assuming it survives legal action.

A challenge was announced on Wednesday by independent MP Andrew Wilkie and gay activists. On Wednesday night Alex Greenwich, an independent member of the New South Wales parliament and co-chair of Australian Marriage Equality, said an urgent injunction would be sought to try “to stop the postal plebiscite in its tracks”.

Labor’s Penny Wong, who is gay and has two children with her partner, delivered a passionate speech in the Senate, saying the Australian Christian Lobby had “described our children as ‘the stolen generation’.

"We love our children, and I object – as does every person who cares about children and as do all those same-sex couples in this country who have kids – to being told that our children are a ‘stolen generation’,” she said.

Turnbull’s line is that Australians are capable of a respectful debate.

“I have great confidence in the good sense of the Australian people,” he told parliament.

“Are we seriously at the point where the Labor Party has so little confidence in Australians that they would shut down a right to vote because people have said things they find outrageous or unacceptable, or that are regarded as unacceptable by the vast majority of Australians?”

Regardless of whether we should be having the postal ballot, it’s clear the campaign will see some bare-knuckled brawling.

When Abbott was asked what marriage equality had to do with political correctness, he said: “Well we heard in the Senate today a Labor senator saying that it was somehow wrong to suggest that ideally children grow up with a mother and a father …

"Obviously families come in all shapes and sizes these days … But there is nothing wrong with saying that ideally kids should have a mother and a father. Now sometimes they won’t for all sorts of reasons, but what sort of a path have we come to if what is self-evident common sense can no longer be stated anymore?

"And this is why so many people are anxious about what they think is the war on our way of life that politically correct activists have been prosecuting for years now,” he said.

It could be potentially risky for the yes side if the naysayers can extend the very specific issue of marriage equality to tap into the broader discontents of those who distrust what they see as the elites who are somehow undermining “our way of life”.

Forster, a Liberal City of Sydney councillor, can be as focused and as tough as her brother.

She hit social media early on Wednesday, tweeting: “If you value mutual respect: vote yes. If you want all Australians to be equal: vote yes. If you believe in free speech: vote yes” – and followed up with more. She confirmed she was responding directly to Abbott.

During a round of media interviews, she said the marriage issue “is not about political correctness”.

Forster and her partner Virginia plan to marry.

Abbott – who is close to his sister – for his part countered that she hadn’t always been a supporter of same-sex marriage. She’d said some years ago “that she just got herself out of one marriage, why would she be rushing into another one”, he told 2GB.

A televised debate between the two might rate quite well. “I’d be up for it, absolutely,” Forster told The Conversation. “A fireside chat between Tony and me would be lovely.”