I thought he denied Russia yesterday? CNN of course ignores that......
The problem is that he won't deny Russia's involvement. So, he's likely to lose on that issue. Unless he can show another source, people will agree with the experts who are investigating the leak.
The other problem is that people are questioning the accuracy of some of the emails. If the source cannot be identified and won't come forward, there will likely be a cloud over the content of the emails.
Assange should disclose where they came from so that they will have more value.