The most obvious scenario is eight years of Liddy Dole followed by eight years of Hillary Clinton.
The POD obviously is that something prevents GW Bush from running in 2000. (Maybe he dies in an accident. Maybe there is a spectacular lapse into youthful bad habits. Maybe he loses the 1994 Texas gubernatorial race. Maybe Clayton Williams avoids rape jokes and wins the Texas governorship in 1990; Bush obviously can't very well challenge him in 1994, and winnng the governorship in 1998 won't leave him with enough experience to be a plausible presidential candidate in 2000.) Liddy Dole will of course face plenty of opposition in the GOP primaries--from McCain, Kasich, Engler, Ashcroft, and other possible candidates--but that she can win the nomination and go on to defeat Gore is at least plausible.
Just why HRC rather than Obama would win the Democratic nomination and general election in 2008 in this ATL is something I haven't worked out yet...