I think it's an interesting incongruity.

Democratic policies create an environment more appealing to OC with more opportunity for corruption (eg unions, govt program's) etc but Ironically (and credit to getthesenets) mafia ethos/attitude would I suspect be quite republican. That is, minimal taxation, regulation, free enterprise etc.

So whilst the mafia prefers liberal institutions it is only for the opportunity to corrupt them. Democratic policies are preferable, but only because it affords the opportunity for abuse.

So, whilst the democrats is the obvious answer, it is an interesting paradox deserving of a more in depth response.

Again, getthesenets deserves recognition for raising an interesting and valid perspective.