Reducing art to one element or principle is counter-productive and reductive always, but there are laws and principles that govern art. One of the most important principles is that of "tension and release." Though the Law of Tension and Release applies to all art forms, including poetry, the term is most often applied to music.
When applied to music, "tension and release" often refers to tonic resolution, but even in the realm of music I am not applying it in this narrower sense. Tension and Release is a much broader law or principle.
Here is a piece of music that illustrates the Law of Tension and Release. It is the piece "Boat of Car" by They Might be Giants. (I am using this demo version because I could find no other version on Youtube.) As you listen, consider how tension and release works in this piece.
I chose this example because it so clearly illustrates this law. The very structure of the recording is based on this law. The recording is divided between tension and release very cleanly--the law is rarely illustrated or demonstrated so simply.
Unbearable tension exists throughout the piece until 0:58 when the Release occurs. You may want to listen to the recording several times to get the full effect, though this re-listening will probably not be necessary.
Again, reducing art to one law or principle is unhelpful, but it does help to look at these principles. The principles apply to every art form, including poetry. Poetry follows all the laws of art--one law is not more important than another.