Clinton's 'I didn't say that, but if I did, it would have been a joke' is exactly what politicians say when they said something they don't want attributed to them but aren't sure if there's any evidence of them saying it.

Occam's razor applies here. Your theory is that she had 1. intended to assassinate Assange, 2. attempted to cover it as a joke and then 3. further covering it up by implying she doesn't remember this statement.

Let me offer you another theory: she's almost certain that she didn't say it, but she couldn't remember every word she's said.

Which theory do you think is more likely?

Now I am not saying you are wrong, but you'd need external evidence to support your theory, until then, Occam's rule apply. If you agree that my theory is more probable but do not like it, then it's possible your current belief is skewed by your prior belief.

Using Occam's razor like that is essentially a logical fallacy.

Elaborate? We are discussing event probability, not logical inference, so how can there be fallacy in the first place.

Yes and you are assigning event probability arbitrarily. This is why it is hard to use occams razor correctly in a non-subjective way. I can just as easily say that there is a very high probability that she said it, and doesn't want it on the record. There is nothing backing this as being more or less probable than what you said, it is all arbitrarily subjective prob assignments since we are both going on nearly no information.

That argument is exactly what slanderers say when they know their target didn't say something that the slanderer wants to attribute to them, to distract from the complete lack of any evidence of their target having said it.