Labor and the Coalition have both ruled out forming a government with minor parties and independents. So in the event of a hung parliament, there are only three options:

1. The formal deal

The formal deal works along the lines of Julia Gillard's agreement with the Greens and independents Rob Oakeshott, Andrew Wilkie and Tony Windsor in 2010. Remember the scenes where all the parties sat down, amid much fanfare, and signed in front of the cameras? In this case, the Greens and independents guaranteed "supply and confidence" in Labor, to allow Gillard to go to the governor general to form a government. A formal agreement allows the minor parties and independents to write in policy demands, as the Greens, Oakeshott and Windsor did in the 2010 agreement. The formal agreement has the usual caveats which render the deal broken, such as corrupt behaviour. Both Tony Abbott and Kevin Rudd have ruled out such a formal deal.

2. The informal deal

An informal deal involves the major party negotiating "confidence and supply" with minor parties and independents on a handshake, with no guarantees. That major party would need to convince the governor general that they had the confidence of the parliament. If that was possible, government would have to negotiate each individual piece of legislation through the parliament. Notwithstanding Gillard's formal agreement in 2010, by the end of the three years, Labor was forced into this informal deal when relations with the Greens and Andrew Wilkie broke down. Wilkie withdrew his support in 2012 over the failure of his poker machine reforms. The Greens leader, Christine Milne, ended the party's formal agreement with Labor in February 2013, though she continued to guarantee confidence and supply. Abbott has said he will not enter into any negotiations with the minor parties, suggesting an informal deal is off the table. Rudd has said he will "work with the result of the election", suggesting he could still negotiate an informal deal.

3. Another election

If neither side will negotiate with the minor parties and independents and therefore no party can claim the ability to form a government, there has to be another election. In this case, Rudd, as caretaker prime minister, would visit the governor general to advise of the situation. Legal advice would be sought but it would be up to Rudd to call the election.