The Russians have to make sure Obama gets reelected first... that part's going to be fun to watch. The 'weakening' part? Not so much.
He is just one of the useful idiots to the Russians now. They could care less about him at this point. They got all they could get from him. A good parallel is the Green Global Warming movement. The Russians used the movement to weaken the Wests ability to produce oil. Then they apparently trashed the movement (Climate Gate) when they had a bunch of oil to sell.