If there hasn't been a change in circumstances to justify it, I'm not sure on what basis it would be lowered. Ultimately, you should get an attorney to look closely over the facts of your case to be sure.
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If there is no change of circumstance in either incomes or parenting time, he is unlikely to prevail. An attorney representing you might also successfully argue that you should be awarded attorney fees due to his transparent attempt to revive an objection he failed to file in a timely manner by the filing of a new and frivolous request to reduce support.
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The other answers submitted to your question are correct; there needs to be a change of circumstances to modify child support. However, obtaining a new job justifies a change in circumstances sufficient to modify support in many cases. The issue in your case is going to be: How big is the disparity between what you currently make and what you will make once you start your new job?