A perfect storm of many things led to Donald Trump being elected.
The thing is, if collusion with Russia is ever proven, that will invalidate his victory, yet we can never know if their meddling tipped the scales in his favor nor not.
But, to be clear, if collusion with Russia to get him elected is proven, he (or his campaign) cheated, and he can not continue to be a winner in that case. Just like when an Olympic champion later is found to have cheated...the medal is taken away.
Mueller is coming.
The clown is done.