Nearly halfway through Canada's election campaign, national unity among the most popular parties means distrust of Donald Trump and distaste for a consumer carbon tax.

The economic disruption and sovereignty threats spawned by the U.S. president have transformed a left-for-dead Liberal Party into a dead-centre front-runner and forced the Conservatives to wave the maple leaf in an environment where patriotic gestures are no longer just for people who park heavy equipment in public places.

Mark Car…