Per the OP this Crosby Stills & Nash song seems to talk about a failing relationship (I think) although somewhat cryptically. Is this song a reflection of a (then) real life scenario one one of them was going through?
What’s it all about?
http://www.geocities.com/SunsetStrip/Palladium/1841/sjbe.htm
lyrics link
It’s about Judy Collins, but whether it was CSN or Y or exactly what the deal was with her I don’t remember.
Well since Steven Stills wrote the lyrics we can assume it was about him…
I believe I’ve read that at the time it was written, Stephen Stills and Graham Nash were in compeitition for her affections. Looks like Stephen got one up on ole’ Graham 
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I guess I’m not as much of a Styx fan as I thought. I had no idea they covered that song.
According to the sleeve notes in the limited edition gold cd
The album starts off with this love song to Judy Collins and finishes with 49 Bye-Byes which is two songs rolled up into one, 49 Reasons and Bye Bye Baby and records the end of Still’s relationship with Judy Collins, the whole album could be seen as being inspired one way or another by her.
???. I thought the Styx song was called “Sweet Madame Blue” and was no relation to the CSNY song.
The Styx song refers to a declining America in general, on the world stage (Carter years, and all ya know)