Certainly all of the above, trying a new instrument etc. can help if you are truly stuck.
However, I think you are talking about a lyrical roadblock rather than a musical one. Forgive me if I have misunderstood.
Yes, I certainly have found myself with a line I really like and then struggling to make something with it. It's as if I love this line and don't want it to be "spoiled" by placing it next to inferior lines. It's a classic block!
What is happening is not that you can't think of anything (you already said "lots of ideas" but that you were struggling to bring them together). It is rather that what you think of doesn't fit well enough for your liking - you are self-censoring everything like an overcritical editor.
I have had lines and songs that have taken years to get to the point that I am happy with them. I think Leonard Cohen took 3 years on "Hallelujah".
I think the only way out is to write something. Anything. It doesn't matter if it's not good enough. Once you have something you can work with it and develop it. While it is in your head it is too ethereal. Get it on paper - don't be afraid to throw things away. It will come!
As I said in a recent thread here..
"I really don't believe that it is a matter of waiting for inspiration. I don't think it happens that way very often.
I think when you are working, something happens - and sometimes that feels a bit like inspiration.
So I say - just start. It's that simple. The rest will follow."
Nice line by the way! The word "die" is limited in the number of useful rhymes available, but the great thing is that there are soooo many synonyms and euphemisms available!
BTW, maybe Political Studies isn't really your bag?