The "spying" starts at the point where there's a good chance that Trump will indeed run.....and continuously....likely to the time when Rice FIRST asked for the unmasking and any and all associated paperwork.
It could only have been for political purposes....because that is how it was used...and in particular...Flynn.
No secret....Well known that Clapper disliked Flynn intensely.
Why no scientists, engineers, lawyers, lobbyists...in the mix instead of the list being ALL Trump associates.
All this begs the question, if they were monitoring the Trump campaign, one few political “experts” believed had any chance of ultimate success, what other Republican candidates were under similar or even more intrusive surveillance? Bush? Cruz? All of them? I can’t get my head around them going after Trump as early as October, 2015 when expectations then were still centered around drubs like Jeb Bush. Just speculation, but I think they must have had several campaigns as well as the RNC infiltrated and under electronic surveillance, all with the expectation that there was no way Hillary Clinton could lose.
The timeline is key. If they started spying on Trump BEFORE wikileaks announced that they had gotten Democrat emails (and the subsequent allegations of Russian hacking), then they had NO REASON to start surveillance of Trump's communications other than for political purposes.