The turmoil on Wall Street and the weakening economy are changing the contours of the presidential campaign map, giving new force to Senator Barack Obama’s ambitious strategy to make incursions into Republican territory, while leading Senator John McCain to scale back his efforts to capture Democratic states.

Mr. Obama has what both sides describe as serious efforts under way in at least nine states that voted for President Bush in 2004, including some that neither side thought would be on the table this close to Election Day. In a visible sign of the breadth of Mr. Obama’s aspirations, he is using North Carolina  a state that Mr. Bush won by 13 percentage points in 2004, and where Mr. Obama is now spending heavily on advertisements  as his base to prepare this weekend for the debate on Tuesday.

By contrast, Mr. McCain is vigorously competing in just four states where Democrats won in 2004: Pennsylvania and New Hampshire, followed by Wisconsin and Minnesota. His decision last week to pull out of Michigan reflected in part the challenge that the declining economy has created for Republicans, given that they have held the White House for the last eight years.

But Mr. McCain’s abrupt decision, which caught many members of his own party by surprise, also underlined the tactical political squeeze he finds himself in: by using his fund-raising advantage to compete in so many places, Mr. Obama has forced Mr. McCain to spend money to hold on in what had been viewed as safe Republican states, like Indiana and Missouri, while limiting Mr. McCain’s ability to play offense on Democratic turf.