"I would like to respond about the tax increases," she said when the topic turned to subprime mortgages. "I want to go back to the energy plan," she said at another point, sidestepping another discussion of taxes.

The Obama and McCain campaigns have agreed to an unusual free-flowing format for the three televised presidential debates, which begin on Friday, but the McCain camp fought for and won a much more structured approach for the questioning at the vice-presidential debate, advisers to both campaigns said Saturday.

At the insistence of the McCain campaign, the Oct. 2 debate between the Republican nominee for vice president, Gov. Sarah Palin, and her Democratic rival, Senator Joseph R. Biden Jr., will have shorter question-and-answer segments than those for the presidential nominees, the advisers said. There will also be much less opportunity for free-wheeling, direct exchanges between the running mates.

McCain advisers said they had been concerned that a loose format could leave Ms. Palin, a relatively inexperienced debater, at a disadvantage and largely on the defensive.

The wrangling was chiefly between the McCain-Palin camp and the nonpartisan Commission on Presidential Debates, which is sponsoring the forums……

The debate formats were negotiated by Senator Lindsey Graham, Republican of South Carolina, representing the McCain campaign, and Representative Rahm Emanuel, Democrat of Illinois, for the Obama camp. A handful of aides from both camps were also involved, hammering out issues between themselves and then holding conference calls with members of the commission to reach final agreements, people involved in the process said.