Where did you find those numbers at? And is that residents or measurements of the people who work in DC? There are residents who are retired, don't work, or work outside of DC. Likewise, people in politics may choose not to actually reside in DC itself.
I'm seeing 364,000 direct gov't employees, but 960,500 in "professional, business and other services" which could be anything like banking or marketing, 457,300 in education and health care, etc.
https://wtop.com/business-finance/2018/02/exactly-many-washingtonians-work-federal-government/
Read your own source:
The office's monthly report said, as of November 2017, the federal government directly employed 364,000 people in the D.C. area. About 54 percent of those jobs were in the District itself.
AND THEN:
Local government employment is a close second, employing just shy of 341,000 people in the D.C. metro — up 2.8 percent from November 2016.
So, that's 700k people directly in government alone. We don't have exact numbers for how many of that 960k is employed in lobbying firms, yes.
But, let me put it this way:
https://www.opensecrets.org/lobby/
There are 11.5k registered feaderal lobbyists(These are businesses not people) in D.C. Each of these lobbyists have their own firms and staff that is, if anything, greater than the thousands of people that each of the hundreds of congressmen employ. And their firms are mostly going to be based in D.C. for obvious reasons. And then these lobbyists have consultants that they work with who have their own firms but aren't called "lobbyists". My point is, it beggars belief that the 960k in professional business isn't mostly tied to the lobbying industry in one way or the other. This also isn't even to talk about DNC and RNC firms, advertising firms that are there to get that sweet campaign cash, and otherwise.
In either case, I believe I've sufficiently proven that, if you were to do a completely random sample in D.C., you're gonna have a large percentage of political operatives.
If you do a completely random samples in D.C. Democratic primary voters, you're gonna have a large percentage of those be political operatives for the democratic party.