1998 Without Impeachment and 2002 Without 9/11

[Blackacre]

This is a two-parter. 1998 and 2002 are notable for being the only midterms since FDR that benefitted the incumbent party. In 1998 it was due to an unpopular impeachment and in 2002 it was because of the rally around the flag effect post-9/11.

What would the House and Senate races have looked like had those events not occurred? Had 1998 and 2002 just been normal midterms, how would the races have gone? Would the House have flipped in 2002? How much could the GOP have gotten in 1998?

For the sake of simplicity let's take the two events in isolation of one another, rather than a 2002 without 9/11 after a 1998 with no impeachment.