The Iowa caucuses are arguably the most difficult assignment for any pollster. That is because relatively few people attend them, and people can, and do, change their minds in the caucus room.
Any poll done ahead of that faces the challenge of finding likely caucusgoers and gathering enough data to assess the “what ifs?” of caucus night. I’ve said many times that it should not be possible to be accurate in polling caucuses. All we can do is take our best shot.
For the past several caucuses, that’s worked out OK for the Iowa Poll.