This would never happen. As far as I know, the US has never had a violent change of power except for the Civil War and former Presidents and their spouses are protected for life by the secret service. When the guy you want to target is very well known and knows the country's deepest darkest secrets, there's nothing you can do.

Everyone else, however, well... we won't be so lucky.

Edit: And no, it is they who must trust us. We must never trust them and we must always be vigilant, always looking over their shoulder, ready to squash their wretched political careers at the slightest infraction against democracy.