Washington ? Barack Obama and John McCain will both pursue the image of a strong leader in troublesome economic times as they meet tonight for their third and final presidential debate.

Their face-off comes as Obama widens his lead in typically Democratic states and campaigns with an air of optimism about his prospects, while McCain seeks a way to gain ground and finds himself defending traditionally Republican states with less than three weeks left in the race.

“We cannot spend the next four years as we have spent much of the last eight: waiting for our luck to change. … As president I intend to act, quickly and decisively,” McCain said Tuesday in battleground Pennsylvania. There, he unveiled new economic proposals and previewed a possible debate strategy: argue that he would be different from Bush and better than Obama.

One day earlier in swing state Ohio, Obama outlined his own economic plan and showed off his own pitch. He suggested that McCain was more of the same and that putting a Democrat in charge was the only way to fix the economy’s woes: “It will take a new direction. It will take new leadership in Washington. It will take a real change in the policies and politics of the last eight years.”

Tonight’s debate at Hofstra University in Hempstead, N.Y., is slated to focus entirely on the economy and domestic policy. The candidates will be seated at a table with moderator Bob Schieffer of CBS.