What type of support would I use for a hutch that is leaning inward?

Question

I have a hutch that is comprised of two pieces that come together. The bottom is a flat surface with a cabinet and two doors in addition to some storage space. Above it, is a more storage space alongside a small cabinet with a glass door. The top portion looks like a lower case N that is arched up. The issue is that it has been taken apart several times because I've moved it to the different places I've lived. The top cabinet and small storage space are closing it on itself and the whole top portion of the hutch is wobbly which is unsafe, obviously. Any idea of how I should support it, perhaps a 2x4 or 2x3?