First of all, the former government of Spain lost ITSELF the election. The soundbite that the US media is trying to foist on us is that "The Terrorists" wanted a change in government and the compliant Spanish gave it to them because they were chicken shit.
What actually happened was that the Spanish government tried hard to blame the terrorist attacks on Basques and use ethnic prejudices within Spain to their own political advantage. When the people of Spain saw through that, they did the right thing and voted the bastards out of office.
Anyway, a terrorist attack in the US prior to election day probably should not change how you vote. Once a large-scale terrorist attack happens, there is necessarily a period of retrenchment and regrouping. There will not be another major terror attack for a good long while, more than enough time for a government transition to take place.
I think non-viable others are not good choices on foreign policy. I think Kerry is a wiser choice than Bush, but some will disagree with me.