Prime Minister Malcolm Turnbull may be forced to call an election after just two years of the Coalition's current three-year term, political hardheads believe.

Senior figures in the Liberal and Labor parties confirmed to Fairfax Media on Monday they are working to be "campaign ready" by June or July of next year, with an August or September election firming as the most likely window for the next national poll.

The problem for Mr Turnbull is a logjam of fixed-date state elections in 2018 and early 2019, and a constitutional requirement for senators who were elected to half-terms at last year's double dissolution election to face voters again.

The Victorian election campaign will run from late October 2018 up to election day on November 24. South Australia, Tasmania and Queensland are also due to hold elections in 2018.