Fresh from the Republican convention, Senator John McCain’s campaign sees evidence that his choice of Gov. Sarah Palin as his running mate is energizing conservatives in the battleground of Ohio while improving its chances in Pennsylvania and several Western states that Senator Barack Obama has been counting on.

Mr. Obama’s campaign intends to focus heavily on the economy, especially in light of the mounting job losses, and to keep up the effort to tie the McCain-Palin ticket to the policies of President Bush. It is banking on holding all the states Senator John Kerry won in 2004 and picking up the additional electoral votes it needs by flipping some combination of Ohio, Nevada, New Mexico, Colorado, Indiana, Iowa and Virginia into the Democratic column.

With just over eight weeks left until Election Day, the two sides are settling into an unusually broad set of state-by-state face-offs, with an increased focus on turning out supporters and tough decisions looming about where to invest time and money for new advertisements.

Yet the two men issued a joint statement on Saturday announcing that they would appear together at the World Trade Center site on Thursday, an idea that aides said originated last week when Mr. Obama called Mr. McCain to congratulate him on accepting the nomination.