Options for the federal election

WHAT'S POSSIBLE

* The first possible date for a normal House of Representatives and half-Senate election is Saturday August 6, the last January 14, 2017.

* A House-only election could be held before August 2016, but a half-Senate election would be needed by May 13, 2017.

* The last opportunity to call a double-dissolution election for the House and all of the Senate is May 11, the day after the budget.

* A double-dissolution election could be held before June 30 but that would backdate Senate terms to July 1 2015, resulting in the need for a half-Senate election between August 2017 and May 2018.

* The more likely date for a double-dissolution election is July 2, following a seven-week plus campaign.

PREVIOUS DOUBLE-DISSOLUTION ELECTIONS

* Joseph Cook called one in 1914, and won five seats.

* Robert Menzies in 1951, lost five seats.

* Gough Whitlam in 1974, lost one seat.

* Malcolm Fraser in 1983, lost government.

* Bob Hawke in 1984, retained government with a reduced majority in a bigger parliament.

* Hawke again in 1987, won four seats.

THE CASE FOR A DOUBLE-DISSOLUTION ELECTION IN 2016

* For the government, it clears the decks of recalcitrant crossbench senators. Under planned changes to the way Australians vote for the Senate, crossbench numbers are likely to fall from eight now to two or three - possibly all from the Nick Xenophon group.

* The coalition is likely to win half the seats in the Senate, with Labor, the Greens and the Xenophon group sharing the other half.

THE CASE AGAINST

* Lack of plausible triggers: So far only two pieces of government legislation - abolition of the Clean Energy Finance Corporation and new governance rules for trade unions - have been rejected twice by the Senate.

* The mechanics of calling one: the post-budget day deadline; requiring parliament to fast-track money bills; a long and arduous election campaign with the potential to antagonise voters.