MEMO to Republican legislators biting your nails over the New York primary, wondering if you can finally derail Donald J. Trump’s candidacy with, gulp, Ted Cruz: You brought it on yourselves.

Not just by failing for too long to take Mr. Trump seriously or by lacking an effective response once you did. That’s well-covered territory. Most important, you created the anger that lifted his candidacy by years of systematically and effectively preventing passage of legislation that might have ameliorated the tough economic state of Mr. Trump’s core voters.

Mr. Trump’s biggest supporters are disproportionately white, middle-aged, working-class men without college educations, a group whose fortunes have flagged as globalization and new technology have rendered millions of jobs obsolete and cut into the wages of many more. While the trade agreements that Mr. Trump bashes have played a role, the mistake was not having entered into them, but having failed to sufficiently help affected workers adjust to the new dynamics.