If Tony Blair is remembered in history only for his support of the Iraq War, that will be a tragedy. The former British prime minister was one of his generation’s most important political leaders, bringing the left out of the wilderness and reshaping it for the post-Cold War world. He remains remarkably prescient about politics. About a decade ago, he began explaining that the most significant political divide of the future was not between left and right, but between open and closed.

To understand this notion — which has been written about smartly by David Brooks and Alec Ross as well — take a look at what has happened to the Republican Party. The GOP has been split apart not on a left-right divide but on an open-closed one — between those who favor free trade, immigration and technological dynamism, and those who worry about these forces. Polls show that Republicans are now more opposed to free trade than are Democrats.

This open-closed divide has produced cleavages in left-wing parties as well. Britain’s Labour Party is bitterly divided between its open, Blairite wing and its closed old-left cadres. The U.S. Democratic Party has experienced the rise of Bernie Sanders, though it remains relatively united.

Many see November’s election as a strange anomaly, a one-off. But it might be a harbinger of a political realignment, with the Democratic Party increasingly representing technocratic elites, college-educated professionals, working women and minorities, all with an open orientation toward globalization. The Republicans are becoming the party of rural districts, blue-collar workers and mostly less-educated, elderly white men — who support a closed system of controls on trade, immigration and perhaps even technology.

For those of us who believe in openness, it seems obvious that the answer to our problems is not to erect barriers to trade and investment. We live in a deeply interconnected world economy with global supply chains. We can’t reverse these trends. Most “American” products today are actually sourced, made and assembled in many other countries. Slapping tariffs on one or two countries — Mexico and China — won’t bring jobs back to America. It will send them to Peru and Vietnam.

But how to respond to the very real concern that the free movement of capital, goods, services and people has not benefited the average American worker?

The answers can be found in research by Edward Alden and Rebecca Strauss and by a team at Harvard Business School. They point out that the U.S. economy’s relative position has actually improved in recent years. Over half of the world’s top 100 companies are now American, and those that dominate the digital age — Google, Facebook, Amazon (whose chief executive, Jeffrey P. Bezos, owns The Post) — are almost all American. But the United States has not invested nearly enough in its workers — in their skills, education, infrastructure and access to capital — so that they prosper along with the country’s corporations.

For example, Alden and Strauss note that the U.S. government spends a pittance on job retraining and related measures: 0.1 percent of gross domestic product, compared with 0.8 percent in Germany and a staggering 2.3 percent in Denmark. The United States spends a lot on education, but inefficiently and mostly for already wealthy and well-prepared children. Infrastructure is bad and public transportation worse, so workers cannot move easily to new jobs. These kinds of investments would allow American workers to share in the prosperity of the general economy.

The smart politics of the future will prioritize being “open and armed,” willing to compete in a global economy and equipped with a bristling armory of tools and training. It will require a far more ambitious set of government programs. We will need retraining on the scale of the GI Bill, available to any worker at any point in his or her career. Anyone who works full time should make a decent wage. The simplest way to implement this is the wonky-sounding but amazingly effective policy called the earned-income tax credit — by which the government tops up the wages of anyone working full time. Perhaps eventually we need a universal basic income, to replace an outmoded and inefficient welfare state.

Sanders has often said that the United States should look to countries such as Denmark and Sweden and emulate their economic policies. It’s a good idea. But he may not realize that all Scandinavian countries are staunch free-traders — in fact, they score higher in trade freedom on the Heritage Foundation’s Index of Economic Freedom than the United States. All take in immigrants generously. Sweden even has a higher percentage of foreign-born people than America does. But these countries combine this openness with strong, effective policies that give their citizens the skills, capital, infrastructure and breathing room they need to succeed in the world. The countries of Scandinavia are more open than America and much better armed.

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