“Separation” —
Not plausible deniability.
It would be like Putin’s former campaign manager heading an anti-Obama operation in the USA in the 2012 election.
And Putin would say, “He’s his own man. I didn’t know anything about it.”
Putin may know about it, but the other guy still “stands on his own” and that person will have to abide within the laws of the country he is in.
There is NO VIOLATION of the law, simply because Putin knows about it, or that the guy used to work with Putin in the past.
As you very well know, these “campaign operatives” will float from candidate to candidate, over the course of their careers. They won’t usually switch parties, but they will switch candidates with every election ... :-) ...