Their evidence? The hacks “are consistent with the methods and motivations of Russian-directed efforts.”
So they claim Russia is guilty of all the hacks based only on the idea the hacks are similar in style to other hacks they believe were done by Russia?
Well what if they were wrong about the earlier hacks they thought were by Russia but was really someone else?
What if someone was just mimicking Russian techniques to throw off the trail?
This is pure speculation, and as such, Trump is correct to say the comments were purely political in nature.
That said if it was the Russians, who can blame them? Clearly Obama has been extremely hostile to Russia and Hillary has been talking like she wants to return to the days of the cold war.