John McCain tonight faces the task of using the final presidential debate to turn his campaign around and persuade US voters that his economic plan, rather than his rival Barack Obama's, is their best protection against financial uncertainty.

The two candidates meet in Hempstead in New York State for their third and last televised encounter before the election in three weeks' time. Opinion polls gave Mr Obama the edge in two previous debates as the financial crisis deepened. Democrats have historically been more trusted by voters to handle the economy.