Manafort was the Campaign Chairman for the Trump campaign.
Manafort pleaded guilty to conspiracy to defraud the United States in connection with his failure to register as a foreign agent.
Manafort gave polling data to someone associated with the Russian government.
These are indisputable facts.
When did it become illegal?
It became illegal when Manafort and/or anyone associated with the Trump campaign decided to give that information to a foreign government in exchange for help in electing Donald Trump
I don’t care what Putin or the Russian government did with the information. The act of sending that polling data is a crime, in my mind.