Bill Shorten says hanging onto the Tasmanian seat of Braddon will be "tough" for Labor, as he adjusts expectations ahead of the July 28 poll.
Labor is fighting to retain Braddon and Queensland's Longman, as Mr Shorten tries to avoid being the first opposition leader to lose a seat to the government at a by-election in 98 years.
"If we win that will be huge. It is a tough contest, no question," Mr Shorten told reporters on Monday.
"Anyone who says an election is in the bag, I think we just need to remember that the voters still have to make the decision."
Labor won Braddon in 2016 but Justine Keay had to resign due to her dual citizenship, and Mr Shorten admits it will be an "uphill battle" to hold onto the marginal seat.
Susan Lamb is also trying to retain Longman for Labor, after she too was forced to resign over her citizenship.
