How might the workers at a factory in the northeast react to the lowering of the tariff?

By definition, tariff is a tax that is imposed in the imported goods and services. If this is lowered, the state in which the goods and services are sent to will get only very little amount. The senders will then be more encouraged to send the goods and there will be greater chances of competition with the good produced on site itself. Thus, the worst case that could happen is that the workers might end up losing their jobs.