At Tuesday’s debate, Kamala Harris, the vice president, will try to promote herself as a change candidate without criticizing President Biden, whom she has served for years.Vice President Kamala Harris will try to use her debate on Tuesday against former President Donald J. Trump to argue that Americans are ready to turn the page on the politics of the past decade, with its turmoil and social animus.But Mr. Trump, standing just feet away, is likely to make a different case: He is expected to try to paint Ms. Harris, the sitting vice president, as the candidate of the status quo.The...