From Howard Fineman of Newsweek:

...The second and third presidential debates will shift the focus - the second, part way to domestic matters; the third, all the way. Bush's aim will be to paint Kerry as an unpalatable liberal who accumulated nothing but bad Big Government ideas during his 19 years in the Senate. Kerry will answer, essentially, "I'm a Democrat." In normal times that would not be a good enough answer, but if the tide of dissatisfaction with Bush as commander-in-chief rises high enough, being a Democrat - in other words not George Bush - may be good enough.