Does " DC insider" mean "Washington DC insider/US politics insider"?

An insider probably comes from people in jail. Or not. Regardless, if you're an insider in any institution, you know who to talk to about what. He's made friends with sympathetic ears and ideologies.
In detail here, most likely means policy. He's ingratiated his ideals into law or party platforms. I believe he's a member of Congress. He probably doesn't believe in helping his fellow man. Like taking care of them when their down, so he and his ilk have overlooked signing a bill that would prolong unemployment benefits. Now the people have nothing and he's happy.
His plan worked. He'll show the poor who's boss.

Thank you Ceili.
What does DC stand for?

The city of Washington is under direct federal control and is not part of any state and DC stand for the federal District of Columbia.

DC is also useful in telling apart the Federal city of Washington DC from the west coast state of Washington.

PS Washington DC first name was Federal city before being rename after our first president.

Insider has nothing to do with people in jail. It means someone who knows influential people, or wants people to believe that they know influential people; it means someone who knows how the power structure works, or wants people to believe they know how the power structure works.

Insider is a commonly used noun which means someone who knows how a group, an industry or an organization works, or who knows those in positionos of power. A health care insider would be someone who works in the health care industry and knows how things are done. A banking insuder would be someone who knows how things are done in the banking industry. It is often implied that the insider him- or herself wields power and has influence.

One might write:

"Stock prices of American auto manufacturers have been slipping on Wall Street and other stock exchanges for weeks now. Industry insiders say this is both because of the lukewarm response to the new model year, and the resurgence of Toyota to the number one spot, world-wide."

The industry insiders are implying that they know things the general public doesn't understand. It's not always true.

That's the first thing I thought, but didn't want to get into it.

DC stands for Washington D.C. or District of Columbia.
The capital of the United States.

It was a glib comment. I have no idea who used it first or in what circumstances. I doubt if anyone really does. One source said the stock market, who knows?
The reality is, it's not always an important person or even someone revealing important stuff. I've just read two articles written by "insiders" in the Mormon Church and from the fashion world.
Or it can be very important, Undercover cops go inside a criminal gang, whistle-blowers, ike Snowden, were insiders who leaked info they were privy to, giving you an insight into the insides of the NSA.