Donald Trump isn’t the first politician to call for a rewrite of the North American Free Trade Agreement­. In the 2008 Democratic primary, both Hillary Clinton and Barack Obama agreed that it made sense to leverage a U.S. exit to renegotiate the pact.

Proponents of a do-over argue that the trade pact has mostly helped Mexico, drawing U.S. factories and jobs south, where labor is cheaper. While some attorneys said that a renegotiation could potentially save U.S. jobs while not necessarily hurting Mexico, others said that leaving the pact altogether would hurt U.S. trade for a multitude of reasons.