For some reason, I am unable to partition my SSD.
Disk Utility reports a small amount of disk space, but this is a known issue to do with local snapshots:
Note: You may notice a difference in available space statistics between Disk Utility, Finder, and Get Info inspectors. This is expected and can be safely ignored. The Finder displays the available space on the disk without accounting for the local snapshots, because local snapshots will surrender their disk space if needed.
I actually have plenty of free disk space:
Best Answer
You can disable local snapshots with
sudo tmutil disablelocal(and then you may have to wait a while for all of them to be deleted and the space freed). I'm not certain that's the entire problem, since the error ("The target disk is too small for this operation") isn't what I'd expect to see for a lack of free space issue. But it's worth a try...I'd also be sure to update your real backup before turning off local snapshots and/or repartitioning. And when you're done, be sure to turn local snapshots back on with
sudo tmutil enablelocal