Momentum is building in senior Liberal Party ranks for a conscience vote on gay marriage if Tony Abbott secures the keys to the Lodge later this year.

High-profile movers in recent weeks have included Western Australian Premier Colin Barnett, whom Abbott views as a role model, the Federal Young Liberals and last year New South Wales Premier Barry O’Farrell. But the strong views of two gay preselected inner-city federal Liberal candidates — that could prove crucial to shifting momentum on the issue — have so far fallen under the radar.

Melbourne Ports, currently held by Labor’s Michael Danby, could conceivably tip the Liberals’ way if enough Greens voters decided to preference a candidate with progressive views — preselected Lib Kevin Ekendahl says he will agitate in favour of a conscience vote. So will the candidate in Tanya Plibersek’s safe seat of Sydney, Sean O’Connor.

Ekendahl confirmed to Crikey this morning that “as an openly gay candidate I’m not going be to be supporting any legislation that will contribute towards my own discrimination”.

On the current numbers, a conscience vote of federal Liberals combined with a conscience vote of Labor members and crossbenchers would likely pass both houses. But a large Liberal majority in the next parliament would require Labor MPs to be bound to their platform or a greater number of conscience vote-wielding Tories.

Abbott has given off mixed signals on a conscience vote, at one point flirting with the idea of allowing backbenchers a free vote, before moving to a ban on diversity in the lead-up to last September’s showdown on Labor MP Stephen Jones’ lower house gay marriage bill and a twin Senate bill, which both failed. Prominent Liberal marriage equality supporters, including Malcolm Turnbull, voted no because they was bound by Abbott’s decree.

But in inner-city seats like Sydney and Melbourne Ports, which have consistently registered vast majorities in favour of gay nuptials, the issue could prove an electoral tonic.

As Stephen Mayne wrote last year, a preference deal in Melbourne Ports between the Greens and the Liberals could conceivably deliver the seat to Ekendahl, and similar tie-ups could threaten Martin Ferguson in Batman and even Bill Shorten in Maribyrnong.

Ekendahl told Crikey he was open to negotiations with the Greens: “Melbourne Ports is definitely in play at this election, ideally the Greens are open to preferencing me based on what I believe in.”

But he says extending Liberal preferences in the opposite direction (that likely wouldn’t be distributed) would be a different matter. “Those sort of decisions are made by the federal secretariat, ultimately the decision is made by Tony Abbott and state directors, but I’d like to think they’d be open to negotiations,” he said.

In 2010, Ekendahl fell just 0.4 percentage points shy of Danby on primary votes (37.8% versus 38.2%) with the Greens’ Sue Plowright on 20.7%.

Danby, who did not attend the gay pride march in St Kilda earlier this month alongside resurgent state Labor leader Daniel Andrews, abstained from the lower house vote. Last July he said he wouldn’t be preferencing the Greens first on his how-to-vote card in the three-cornered Melbourne Ports contest at the election, telling 7:30 he “could well” place the party last. He did not respond to queries this morning.

Victorian Greens leader and renowned local numbers man Greg Barber told Crikey that federal laws could easily be changed if MPs from both major parties stayed true to their consciences.

“Ironically we need all the Liberals to vote according to their conscience and all the Labor MPs to vote according to their platform and then we can get marriage quality … the same goes for a state parliament incidentally,” he said, claiming the Greens would triumph in Melbourne Ports when they “leapfrogged Labor” at a future poll.

Australian Marriage Equality convenor Rodney Croome says the ball is well and truly rolling. “By allowing a conscience vote, Tony Abbott will increase the vote for candidates like O’Connor and Ekendahl, as well as other Liberal candidates in seats where marriage equality has high support and is a key issue,” he said.

“A conscience vote is about personal freedom and marriage equality is about strengthening families — both things which Liberals should support.”

Last week the federal Young Liberals passed their conscience vote motion, submitted by the Victorian branch, by a dominant two-thirds majority.