As regards the identity of the "whistleblower," so-called, a number of names have popped up.  Though none is a certainty, each matches what is known about the perp and who was in a position to make the claims that are contained in the "affidavit."

The most widely mentioned is Susan M. Gordon.  A career CIA officer, Gordon joined in 1980 and served in a number of positions.  In 2017, she was principal deputy director of National Intelligence in the Office of the Director of National Intelligence (DNI).  She was slated to take the top position, but evidently, President Trump had his suspicions and decided to look elsewhere, despite threats from the Senate.  (The deputy director by law expected to step into the top slot as a matter of course.)  She resigned from the position last August 15.

Another name mentioned is Michael Barry, former senior director for intelligence programs for the National Security Council.  Barry served in the USAF during the 1980s, where he specialized in intelligence.  He was brought into the NSC by then-director H.R. McMaster.  He left his position in July of 2017 after John Bolton took over, though it was said to be on "good terms."

The third name to attract attention is Eric Ciaramella, an intelligence officer specializing in Russia and Ukraine.  He was a staffer on the National Security Council, where he was responsible for policy regarding Ukraine.  He was H.R. McMaster's personal aide and during the Obama administration had worked with Susan Rice.  Ciaramella had gained a reputation as an inveterate leaker, which, he claimed, had resulted in "death threats" from "right-wingers."  This was the reason he gave for leaving the NSC in 2017.

There's no smoking gun here.  It could be one of these people or someone else entirely.  Barry and Ciamarella were both associated with NeverTrump H.R. McMaster.  Gordon and Ciamarella appear to have some grounds for holding grudges.  On the other hand, Barry and Ciamarella both left in 2017, long before the phone call in which Trump committed his crime against humanity — which does not mean that they became unplugged from the grapevine and may not have heard it at second or third hand.

It remains speculation at this point.  But, as we said yesterday, it's only a matter of time.