Give The Donald his due: rarely is there a dull moment at a Trump rally. Last night at Geneva, Ohio, he ruminated on his “America First” economic policy. Mr. Trump returned to his protectionist message that companies moving manufacturing jobs out of country would be subject to a 35% tariff at the border. The he added a twist with the potential to reshape American enterprise.

“Our good jobs are going to other countries. So we’re going to stop it. It’s not even hard to stop it. And when they know there is that kind of a consequence, they’re not leaving, they’re staying,” Trump reiterated. Then, almost nonchalantly, he added: “They may go to a different State, and that’s different. Right? But they’re staying, they’re staying in our country.”

In a stroke of ostensibly unconscious genius, he recast a problematic policy into the promise of voluntary interstate competition, shorn of federal coercion. Free marketeers have always chafed at Mr. Trump’s protectionist program, which goes against every laisser-faire tenet of free trade, comparative advantage, and consumer choice. Yet they were faced with the fact that jobs were fleeing to foreign jurisdictions, leaving displaced American workers with few alternatives.

Mr. Trump assuaged these misgivings by focusing on currency manipulation, promising to bring forward legislation against Communist China and marking the Federal Reserve’s own easy money policies for contributing to what he calls in America a “false economy.” The limits of this demarche in enthusing voters were evident. Something more, to capture the imagination and spirit of American initiative, is needed.

This is the context in which Mr. Trump’s ostensibly off-hand aside could alter the debate. It can be seen as a call on the States to echo his own pro-growth platform by competing with each other for jobs, by eliminating punitive taxes and removing regulatory restraint. It’s particularly noteworthy, coming, as it does, from a tribune from New York, which has one of the most regulated and highest taxed economies in the country.

Many States are already well on their way, having adopted right-to-work legislation that permits workers the choice to join unions and not be compelled to remit a portion of their salaries for union dues. RTW states allow employers and employees to negotiate contracts and other work-related issues free from union intimidation. A recent Competitive Enterprise Institute study shows that “RTW laws tend to lower union presence, reduce the adversarial relationship between workers and employers, and make investment more attractive.”

On the other hand, minus RTW legislation, “the lack of complete worker freedom to contract individually may be a factor in the out-migration of labor from a state. More importantly, legislation favoring labor unions raises labor costs and makes employers less likely to invest.” Without this investment, the report notes, capital accumulation, productivity, wealth creation, and the prospects for greater employment opportunities all suffer.

The American Legislative Exchange Council confirms these findings. Not only do RTW laws enjoy majority support (71% to 22%), but “right-to-work states outperformed the forced unionism states in both gross state product growth (58.8% to 44.3%) and personal income growth (57.9% to 45.8%).” W0rkers are voting with their feet. ALEC’s 2016 Competitive Index records migration to states like Texas (1st) and Florida (2nd) from California (49th) and New York (50th), corroborating that states reap rewards with entrepreneurial-friendly legislation that signals “we are open for business.”

Contrary States, wedded to regimes of high taxes and regulatory burdens, will reap their just deserts in business decline, lower tax yields, and out-migration. Political survival will compel elected officials to follow in the steps of successful states or face dire consequences of voter rejection or worse: underperforming states must conform or die.

Trump’s interstate enterprise remark also confounds his Republican critics who denigrate his conservative credentials and his fidelity to constitutional principle. Unlike Franklin Delano Roosevelt’s New Deal administration, that sought to set the future course of twisting the Commerce Clause to enforce centralized economic planning from Washington, Mr. Trump returns the clause to its original intent at the time of ratification.

That was removing trade barriers between the States (and consolidating laws for foreign exchange). “An unrestrained intercourse between the States themselves will advance the trade of each by an interchange of their respective productions,” Alexander Hamilton framed the issue in Federalist No. 11, “not only for the supply of reciprocal wants at home, but for exportation to foreign markets.”

Mr. Trump’s advocacy of state dynamism echoes constitutional practice from the time of the Founding, when tariffs were a key source of revenue. The Republican nominee spun a problematic policy of national protection into a competitive proposal for success across the States. It remains to be seen whether Donald Trump can, Rumpelstiltskin-like, turn his once embattled campaign into electoral gold.

Mr. MacLean runs the Disraeli-Macdonald Institute.