Just a hunch, but I would guess that every Senator imagines they have the integrity and courage to stand up and vote their conscience in the face of death threats.
So, why would they let their votes on gun regulation be swayed by NRA's threats to make their re-election difficult?
For some reason, they are more afraid of losing an election than being murdered?
If that is the case, then the campaign launched tonight by Gabby Giffords in an op-ed in the New York Times may turn out to be their worst nightmare.