If I and the other constituents of my district elect a representative to a government office and then it is later discovered that a foreign government previously collected coercive personal information on that representative and used it to benefit the country it represents at the detriment of the citizens that elected that representative, then that most certainly constitutes a unilateral action that has "a direct, immediate and lasting impact on a large segment of civilian, non-affiliated, non-combatant, non-hostile persons."
The only reason blackmail works is that the target wants to keep that information private. Anyone who discovered the information could release it, including press. I think we can agree that releasing the information is thus not an act of war, so the target acquiescing to blackmail means they themselves are choosing to elevate the situation, not the foreign blackmailer. Hence, blackmail is not an act of war.
It certainly can be argued, but I don't think it does by definition.
My problem is that your distinction is false between foreign power and native power. If the same coercive actions (soft blackmail like with Rep. Wiener or Chappaquiddick etc...) are taken by other politicians or croneys seeking power in the same nation, people don't raise nearly the fuss - that's just "politics." See: Every negative election everywhere.
I make no distinction - the end goal is that one group has more "power" or access over the others. Literally impossible to get rid of this quirk of politics with our biology. Making those things "Acts of war" is just untenable.
