Is the “Beltway Stop" a popular metaphor meaning a concurrence of events or things?

I'm interested in the phrase, “Beltway Stop in the Oscar Race” which is the title of an article appearing in December 21 New York Times. It comments on the concurrence of movies focused on the country’s politics in Oscar prize race as follows:

“In the last few weeks Washington and its corridors of power have become an unusual second front in the annual battle for Hollywood’s best picture Oscar. No fewer than three leading contenders — Lincoln, Zero Dark Thirty and Argo — have found their prize campaigns entwined with the nation’s politics.”

OALED defines Belt-way as 'an AmE - a Ring road, especially the one around Washington DC.' But I surmise that “Beltway stop” here implies a succession of events or things, represented by the concurrence of three politics-focused films as contenders in the Oscar race. I wonder if this expression is used very often in writing and conversation, or just a nonce-word invented for this specific article.

Additionally, why is the ‘stop’ in singular form when there are three political-theme contenders (instances) of “Lincoln,” “Zero Dark Thirty” and “Argo” in the Oscar race?

It's not a common idiom, and I'm a little puzzled as to the writer's intent here.

The Beltway is a key highway in Washington DC, so "Beltway" certainly just refers to Washington itself.

"Beltway Stop" may be an allusion to a "pit stop" in a racing track - a refueling/refitting point in the race. This fits the race metaphor, but I don't see how the movies are refueling/refitting.

It may also be related to "bus stop" (as StoneyB said in a comment) - a stop along the journey to the Oscars. This is more in line with a statement later in the article referring to the "Oscar trail's detour into Washington", but it doesn't quite fit with the race metaphor and I'm not really sure how the movies are supposed to be 'pausing' in DC.

In short, I think it's a weird choice for a title.

The Capital Beltway is a freeway encircling Washington, D.C., and as Peter's comment states is often used as a metonym for the Federal Government and the associated Establishment. "Inside the Beltway" thinking, for example, refers not just to the opinion of members of the government, but to the consensus of the journalist/lobbyist/pundit class that lives there. ("Outside the Beltway" is alleged to be the opposite, although the editors of the blog of that name seem mostly to reside inside the Beltway.)

There is also a "Capital Beltway" station on the trunk railway line that goes from Washington to New York and Boston. I believe the author here is extending the metaphor of the Oscar competition as a race by suggesting that it has made a stop at the Beltway, to connect to these particular politics-themed movies.

(Incidentally, the Beltway when under construction was called the Circumfrential Highway. There's a reference by that name in some-or-another early 1960s political novel, that Google won't find for me.)