Malcolm Turnbull's options for an early double-dissolution election on July 2 have narrowed as an unmanageable Senate blocks even the modest goal of having government legislation defeated.
It coincides with the government's withering range of options for tax reform in the lead-up to the election, with previously flagged individual tax cuts to return bracket creep now considered unfeasible while the budget remains so far in deficit.
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Pet issues of the government and the Greens are offered up for debate by crossbench senators on Tuesday.
Treasurer Scott Morrison has told colleagues that only tax cuts that will result materially in higher growth and more jobs will find favour, meaning the winners from the package to be announced in the budget will be companies who get a lowered tax rate.
An insider said the formula would be shaped by the workplace expenses inquiry currently under way and another looking at the definition of superannuation, but cautioned that the overall package was necessarily constrained by the lack of "fiscal headroom" - code for there being no money.
Mr Morrison told a business audience in Melbourne that all policy levers had to deliver growth and jobs and that this was the only way to make tax cuts achievable.
In Parliament, Mr Turnbull again rounded on Labor's capital gains tax changes, saying they would inhibit investment, which was the opposite of what the government was aiming at.
The tight fiscal environment, after dropping the GST option, is being matched by a hostile legislative one in which the government is being denied access to the constitutional "trigger" it most desires to fight an election on - the issue of union militancy and corruption in the nation's building and construction sites.
The legislation, known as the Australian Building and Construction Commission Bill, seeks to re-establish the Howard-era building unions watchdog.
But it has no chance of majority support in the Senate, and now apparently, few prospects of even being debated as the scheduled sitting days run out ahead of the 2016 budget.
The government might want to arrange extra Senate sitting days but cannot compel the upper house, and neither can it enforce what is discussed in the chamber when it is sitting.
The stand-off reached a climax on Tuesday as Opposition leader Bill Shorten took to the National Press Club to outline his approach to the election, revealing Labor will not help it bring the May 10 budget forward by a week to May 3, in order to allow sufficient time after it is tabled to vote through money bills to keep the government running, and to facilitate the ABCC debate.
Amid farcical scenes in the Senate, the government defeated an attempt by the Australian Motoring Party's Ricky Muir to bring the ABCC bill on immediately, because that would have meant delaying debate on the Senate voting reforms. The government has secured support from the Greens party to make those changes, which would have the effect of wiping out most crossbench senators at the double dissolution.
And the Greens were forced to deny another provocation, this time from the Liberal Democratic Party's David Leyonhjelm, who tried to force consideration of the Greens' same-sex marriage reform.
In both cases, debate of the bills was opposed by the party's originally backing them, as the Coalition and Greens sought to ensure the Senate voting reforms would have exclusive room to pass - a crucial prerequisite for a double-dissolution election, which requires smaller election quotas.
The government, with the support of the Greens, steamrolled through a number of those diversionary tactics on Tuesday, weathering ferocious attacks from across the chamber.
Ricky Muir said he was handing the government "on a silver platter" the opportunity to debate its ABCC bill.
"You are putting self-interest before the people of Australia. It's an absolute disgrace," he said.
Labor's Senate leader Penny Wong tore into Greens leader Richard Di Natale for choosing to gag debate on same-sex marriage.
"I've disagreed with various leaders of the Greens but I have to say I've never seen leadership without backbone in the way this one has," she said.
Senator Wong reminded the Greens of their own mantra on same-sex marriage at state and federal level: "Every Green, every vote, every time".
"Every Green, every vote, every time - except today," she said.
With Heath Aston and Gareth Hutchens