Politicians, being humans, do bad things. Sometimes we hold them to higher standards than we hold non-politicians. Sometimes we hold them to lower standards.
What determines the gravity of a particular sin by a politician?
1. How much did it hurt people?
Christie caused really bad traffic, which is very annoying. The traffic may have also contributed to the death of a 91-year-old woman, which is worse than annoying (but also very, very speculative).
Is messing up people's commute for days worse than outlawing their health insurance after insisting they could keep their health insurance? That's a judgment call. Christie's office screwing up people's commutes certainly caused more harm (quantity of harm multiplied by the number of people harmed) than Bill Clinton's extramarital affair in the Oval Office with an intern half his age.
But quantity of harm is not the only factor here.
2. Did someone abuse government power?
Government power is like fire. It relies ultimately on force. We basically give government a monopoly on violence. Nobody else gets to just take your money, lock you up or threaten to lock you up.
So government power is a public trust, and it should only ever be used to benefit the public. When someone uses government power for personal gain or to settle a political score, that's abuse of power. It seems clear that's what happened here.
Even though blocking an entrance-ramp is petty, and even if the harm wasn't huge, this looks like a blatant abuse of government power. That should never be taken lightly.
3. What did Christie know and when did he know it?
The final question is Christie's culpability. Did he know about this abuse of power? Did he lie about knowing about this abuse of power? We don't have answers to that. Hopefully we'll get these answers.