Yes, it can be if appropriate grounds exist. Suppose, for example, that you are responsible for sending child support payments to the other spouse and you lose your job. In this case, you might even request a temporary suspension of your obligations although you would have to repay these obligations after you found a new job.
If the new job pays less, you might petition the court for a permanent downward modification of your child support modifications. There is no guarantee that the court would accept your petition, however.