Denigrate and then emasculate the intelligence agencies, particularly the FBI counter-intelligence department, thus opening the door wide for Russia/Putin to insert Americanized agents into all levels and functions of federal government.
Also bribe, extort, or just convince the most venal and/or stupid of Republican politicians to spread propaganda to support these actions and suppress any countermeasures. The treason being committed against the United States is not just by one man, it is by the entire Republican core.