Not being aware of any evidence doesn't mean it doesn't exist. There is every chance it will turn up, especially if someone rolls over on the others to save their own skins.
There's all kind of things that no one is aware of evidence for. To say that 'there is every chance it will turn up' suggests that there is good reasons for thinking that such evidence exists. Given that the Dems have been pushing this 'Trump collaborated with the Russians' fabricated narrative for months and that not only has no proof of this turned up, no evidence for it has turned up either.
What has happened is that there have been leaks of various bits of intelligence, such as the report of Flynn-Russian Ambassador conversation, that appear to back up this narrative when taken out of context. Who might have made these leaks, obviously designed to look as though they backed up the Democrats fabricated narrative? Well possible answers to that question was provided by Trey Gowdy's questioning of Comey on the question of who could have had access to that data. It was established that
James Clapper
James Brennon
Susan Rice
Loretta Lynch
Sally Yates
Barak Obama
would all have likely had such access.
Like the farce over the recounts and the electoral college I think this will be another case of Wile E Coyote Democrats trying to hit Road Runner Trump and getting hit with their own Acme rocket.