Comment by dredmorbius

Specifics of Russian activities, methods, and US intelligence awareness of same, all of which are relevant.

The fact of the arrest strongly suggests the documents themselves are accurate. If they don't reflect actual Russian activity, they appear to reflect US intelligence of such activity.

If accurate, the documents corroborate a general pattern of activity of election manipulation carried on from at least June of 2016 through November, which would be highly significant.

There is circumstantial evidence of vote tampering in at least North Carolina, based on unexpected vote-tally convergence differences based on precinct size (I'm not entirely sold on the story, though it seems to have some legs): http://www.votesleuth.org/north-carolina-2016-overview/

At a larger scale, this highlights weakensses in multiple elements of liberal democratic institutions, mechanisms, communications, and media, as well as, quite possibly, political bodies and individuals. Arguments which have been in large part theoretical of risks of voting machines, email, and end-to-end encryption are now looking to be substantial, actual, and potentially existential threats.

That's some prime meat in my register.