Trump’s border threats jam up Pence’s trade tour

President Donald Trump’s announcement Thursday that he would be willing to sideline a new trilateral trade pact with Canada and Mexico — a move that would allow him to impose the auto tariffs he has been threatening to unveil — couldn’t have come at a worse time for Mike Pence.

As Trump sat in the Oval Office, telling reporters that border security “is more important to me than the USMCA,” the administration’s proposed replacement for NAFTA, his vice president was hours away from kicking off a multistate tour to promote...