LONDON (AP) — Scotland’s leading politician vied with Britain’s former treasury chief in a heated televised debate Monday, making a final push to capture wavering voters three weeks ahead of a historic referendum on Scottish independence.

Pro-independence First Minister Alex Salmond and Alistair Darling argued and shouted over each other on questions from defense to the sustainability of an economy dependent on revenues from North Sea oil, but the heart of the 90-minute exchange centered on what currency an independent Scotland would use.