> Even if she had been convicted of cold-blooded murder…

Setting aside the moral issues around murder, which give most humans at least a moment’s pause, wouldn’t it be awfully difficult to govern effectively from a prison cell?

> which give most humans at least a moment’s pause

Yes, which is why a murderous candidate would likely lose a democratic election!

> Even if she had been convicted of cold-blooded murder, that should not override democracy.

How do you define "democracy" ? You sound a lot like the people who believe "democracy = voting once every X years".

Judges applying the laws created by politicians sworn in by the people isn't "democracy" for you ?

If the people think the judges are doing a good job, they probably won’t vote for the criminally convicted candidate.

The Le Pen family has been in every presidential elections since 1988 and never won once... she personally lost three of them and is nowhere close to win (~23% out of the 50+ needed)

Her party isn't outlawed so if people like their ideas they'll vote for them anyways.

>Even if she had been convicted of cold-blooded murder, that should not override democracy.

Question, in your jurisdiction, if you are convicted of "cold-blooded murder", are you still allowed to vote?

What if she was born in a foreign country? Or is not even a citizen? Or was under 35?

Should such a person be permitted to run a country?

It's not 'overriding democracy' except by your straw definition.