Historically, for more than 200 years, economists, conservatives, industrialists and western countries have supported free trade, based upon the theories of Smith and Ricardo. Free trade creates more valuable goods and services. Free trade provides opportunities. Free trade forces domestic firms to become more competitive. The losers from free trade can have their losses mitigated through enlightened government policies. Leftists and labor unions have opposed free trade because governments have not always provided those “enlightened” policies to offset the negative effects on workers and because far leftists cannot support any positive results from capitalism.

3 typical pro trade arguments.

Benefits of free trade – Economics Help

Why is free trade good? | The Economist

Why Free Trade? | IFT (ifreetrade.org)

Conservatives in the west have generally supported free trade for these last two centuries. Western firms and their beneficial owners were positioned to benefit (on average) from free trade. Part of this was the justification for imperialism and economic extraction from “less developed countries”, but most advocates saw the local, corporate and global benefits of trade. Republican support of free trade has been consistent in the post WW II era. Most Republican policy wonks agree with their Democratic colleagues that the great depression was deepened and prolonged by anti-trade legislation in the US and elsewhere.

The Benefits of Free Trade: Addressing Key Myths | Mercatus Center

7 Reasons to Support Free Trade – Foundation for Economic Education (fee.org)

The Benefits of International Trade | U.S. Chamber of Commerce (uschamber.com)

Economists of mainstream political views tend to support “free trade” as a government policy which can provide benefits for countries and the global economy.

Is free trade always the answer? | Business | The Guardian

Economists Actually Agree on This: The Wisdom of Free Trade – The New York Times (nytimes.com)

A Super-Majority of Economists Agree: Trade Barriers Should Go | Cato at Liberty Blog

Center for Economic Research and Forecasting | Economists Do Agree on Something! (clucerf.org)

4 Politically Controversial Issues Where All Economists Agree – The Atlantic

The free trade position has been opposed in the last 200 years by many. Leftists and less developed countries see this as gloss to justify exploitation. Marxists oppose capitalism. Labor sees the negative impact on domestic wages. Environmentalists see trade as a way to export pollution. Anti-globalization advocates see trade as a way to provide power to multinational corporations, so oppose it. Supporters of “less developed countries” argue that pure free trade unfairly prevents firms from developing. Incumbent firms argue that competitors have “unfair” advantages, including government support, that must be offset.

Why do economists support Free Trade? | Jobs Back (JobsBack.com)

Free Trade Is Killing American Manufacturing | IndustryWeek

Free trade in economic theories | Exploring Economics (exploring-economics.org)

Economists on the Run – Foreign Policy

The Folly of Free Trade (hbr.org)

While the “science” and “interests” of free trade may be clear, the “politics” is less clear. In a simple, win/lose, Manichean view, evil foreigners attempt to defeat good domestic firms and their employees. Populist politicians of both left and right views are tempted to tap this voting block.

Here’s why everyone is arguing about free trade (cnbc.com)

Failing at Free Trade: Why Economists Haven’t Won the Debate (dtnpf.com)

Finally, 2 articles that consider both sides.

Free Trade Agreement Pros and Cons (thebalance.com)

4 Reasons Free Trade Has Become A Contentious Political And Economic Issue (forbes.com)

As with many modern public policy issues, there is a professionally supported position (pro, with some limits or compensations). However, the gap between the relatively complex analysis (comparative advantage, history, statistics) required to support these conclusions and votes is wide and used by politicians to frame and tell stories in their best interest, not the interest of the nation or its citizens.