I think they're using it in a technical sense that's idiosyncratic to America: "career" members of the Foreign Service Corps, versus "political" appointees that can be directly appointed at higher ranks, but at the pleasure of the (in turn politically-appointed) secretary.
replyThe first might have joined the Foreign Service and worked their way up; the second might have had a career elsewhere (not necessarily in political office), get invited to work for an administration, and then leave once there's a change in power.
> but at the pleasure of the (in turn politically-appointed) secretary
replyParent is correct. The amount varies from administration to administration. But if you really want to be an ambassador, you're well positioned if you bundle a few hundred thousand to a few million dollars for the winning campaign. (There are traditionally limits. You can't usually buy your way into the U.S. Embassy in Baghdad or London. But for the postings with limited security implications, where the focus is on trade, you're mostly hosting expensive parties for your post.)