In the SO moderator nominations, two candidates withdrew their entries after it was revealed that they had been caught using sock puppets with many cross-votes in the past (with the number of fraudulent votes in the hundreds in one case, in the thousands in the other).
Although I was personally a bit sad to see one of those candidates go - I felt that case to be somewhat forgivable - I welcome very much that this information was revealed. It is arguably something that voters have a right to know about.
But the information was published only after somebody commented about remembering having seen the nominee in the penalty box once. @Will then added sock-puppet information about two other nominees underneath their entries (I assume that is a complete list of all nominees with a record of sock-puppeteering.) So the form seems a bit random, and this needs a defined form for the next elections.
Also, users can change their ways, and shouldn't be excluded from elections forever for their misdeeds. Records of past infractions should expire after a reasonable period of time.
I suggest that either
information about past sock puppets with cross-votes (having a sock puppet alone is not a crime!) be published officially, for every candidate, including the number of fraudulent votes the user was caught with. Users nominating themselves will expressly agree to having this information published when entering their application.
Candidates who have a record of vote fraud within the last two or three years (or whatever time span is decided) be silently removed from the nomination page - the more boring, but probably wisest option.