Or someone who came over from one of Trump’s GOP opponents...
I hesitate even to suggest this because it's so off the wall, but your post got me thinking...
There is one person close to President Trump, you mihgt say inner circle, a person who is sought out by TV networks. This person ran a PAC during the primaries that did some very tough anti-Trump ads. they were a bit rough on him.
Now, this person held a significant position in the campaign and works in the White House. this person could be called a Trump insider.
I won't post the person's name, because it's such an off the wall theory that I'm not that sure of it myself, although there might be some external evidence involving someone close to this person that might bolster the theory. You may be able to guess who I'm talking about, or you might not.