With nine days left, Prime Minister Julia Gillard and conservative rival Tony Abbott are having to concentrate their energies on marginal seats where policies on mining and carbon tax, immigration and broadband Internet investment could well determine which way the vote goes. Gillard, campaigning on Wednesday in the key battleground of Sydney's western suburban fringe, tried to focus on her economic credentials. But she had to fend off questions that have dogged her campaign in the wake of a June party coup which unseated predecessor Kevin Rudd.