For the second time, the Senate voted down the government's bill to re-establish the Australian Building and Construction Commission. The government failed to secure the support of Labor, the Greens and key crossbenchers.

What does this mean?

Because it has failed twice, this bill is now a double dissolution trigger. When Prime Minister Malcolm Turnbull announced Parliament would be recalled to consider this and another piece of industrial relations legislation, he committed to a July 2 double dissolution election if the Senate failed to pass either of the bills.

What happens next?

Mr Turnbull has a constitutional deadline of May 11 to advise Governor-General Sir Peter Cosgrove to dissolve both houses. When called upon, Sir Peter will issue writs for a July 2 election (any earlier would mean the next election happening in 2018, rather than 2019). The Prime Minister will probably direct the Governor-General to act after the budget is handed down on May 3, one week earlier than usual.

Could there be any surprises?

Theoretically, Mr Turnbull could immediately advise the Governor-General to dissolve both houses and issue the writs for an election, necessitating the cancellation of the budget. He could also declare he had changed his mind and continue to an ordinary general election between August and November. Both these options are unlikely.

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