As national polling of voter intentions begins to tighten, the Turnbull Government options are also narrowing.
The term of this House of Representatives expires on 11 November 2016 and, writs for a normal half-Senate election cannot be issued before 1 July 2016.
Thus the first available date for a general election would be on or about 6 August 2016 - which would see Parliament dissolved and the Abbott-Turnbull Government in caretaker mode from as early as 21 June, approximately five weeks after delivering its third set of budget papers.
Leaving Prime Minister Turnbull and Treasurer Morrison very little time to tweak any unpopular measures or errors found in their 2016-17 budget before Coalition MPs went on the campaign trail in their respective electorates.
As for a double dissolution. According to Antony Green's Election Blog: