They may have their political differences - but Queensland's Premier and the Opposition leader are now backing the same horse to win the Melbourne Cup.

Anna Bligh's first pick Changingoftheguard has been scratched.

Ms Bligh's second choice is Derby Day winner Roman Emperor - the same horse John Paul Langbroek is tipping.

Meanwhile, UniTab says Queenslanders are expected to exceed last year's total of $27 million wagered on the Melbourne Cup.

A spokesman says early indications are suggesting strong betting.