Populist conservative author and columnist Pat Buchanan says the Republican Party has no “future” should it return to the establishment’s preferred agenda of pro-immigration policies, free trade absolutism, and favoring foreign interventionism.

In an interview with talk radio host Laura Ingraham, Buchanan praised President Trump’s takeover of the Republican Party, where an “America First” approach has been implemented on the key issues of immigration, trade, and foreign policy.

On the latest success for the Trump administration on trade — where the populist president convinced the European Union to drop its trade barriers to U.S.-made goods — Buchanan said it is tariffs, not free trade, that built America’s middle class. Buchanan said:

Tariffs are taxes, but they are taxes on imports. They’re taxes on foreign-made goods, they’re not on American made goods. They’re optional taxes, you don’t pay them if you buy an American made product. And secondly, tariffs are really what built the United States of America in the 19th Century from a country of about three million, purely agricultural, to the greatest industrial power the world had ever seen by the beginning of the 20th Century.

Buchanan said the economic nationalist agenda of the GOP, thanks to Trump, is the only way forward for the party, noting that a return to a pro-immigration agenda, multinational free trade deals, and foreign interventionism would essentially be political suicide for Republicans.

“If they try to go back to open borders and free trade deals and deficits or just ‘Trade deficits don’t matter’ and let’s get into … try to rearrange the Middle East and make it democratic. Frankly, if you get into another major war … I think it’s very problematic for the Republican Party and for its future and for the president,” Buchanan said.

Most recently, Breitbart News‘s Kristina Wong reported that the Special Inspector General for Afghanistan Reconstruction (SIGAR) now estimates that at least $15 billion in U.S. taxpayer dollars were wasted on failed reconstruction projects in Afghanistan.