Why do you care what the Democrats would have thought of a Rumsfield resignation in August or September?
Do you think that they really were planning to vote Republican and that the resignation would jeopardize that?
You have to motivate those who actually might vote your way, not those who never will.
And having Rumsfield resign 5-6 months ago would have motivated those more concerned with the WOT.
The truth is, this Election Day repudiation of the Bush administration really should have taken place in 2004 by all measures. If the Democratic Party hadn't put up a guy who may well have been the worst presidential candidate south of Walter Mondale, it probably would have.