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This section of Election workers: Reporting and withholding | Internal Revenue Service 

says: 

Compensation paid for services and reimbursements paid under a non-accountable plan are taxable to election workers; however, they aren't subject to income tax withholding under Internal Revenue Code (IRC) Section 3401(a). 

If I re-state what you've said and my reading of the above:

 

The wages from the Election Authority are subject to income taxes. Because they (usually) fall under the threshold the Election Authority isn't required to take income taxes out on my behalf, but I can elect to have them. With regards to FICA withholding, whether or not those are owed is dependent on the Section 218 agreement in our state (which for MO is a statewide exception).

Bottom line, I owe taxes on the income?