By Cokie Roberts and Steven V. Roberts

Of all the inane and inaccurate things to come out of President Trump’s mouth, this March tweet was one of the worst: “Trade wars are good and easy to win.” He recently doubled down on that foolishness, tweeting, “Tariffs are the greatest!”

Trump is testing that theory now by initiating trade skirmishes — if not full-blown wars — with China, Europe, Canada and Mexico. And early returns clearly indicate that the president is dead wrong. His trade policies are already causing major ruptures with traditional allies, threatening the economic boom and jeopardizing his party’s prospects in the fall elections.

Many fellow Republicans agree with Sen. Ben Sasse of Nebraska who told USA Today, “Tariffs are stupid. … They’re tax increases on Americans, they don’t work, and apparently we’re going to see more of this.”

Even the president’s closest allies are getting very nervous. The Senate voted 88-11 in favor of a nonbinding resolution that urges a greater role for Congress in setting trade policy, and support is growing for mandatory restrictions on the president.

Sen. Orrin Hatch of Utah, a Trump loyalist, wrote to the president: “I strongly urge you to reconsider the reckless guidance you have received on trade policy from some of your advisers.” Hatch heads the Finance Committee, which has jurisdiction over trade, and he warned the White House, “If the administration continues forward with its over-reliance on tariffs, I will work to advance legislation to curtail presidential trade authority.”

Other Republicans fear that economic damage will lead to political damage in the fall. GOP strategist Kevin Madden says, “There is a significant risk that the benefits of tax reform and the overall good feelings about the economy could all be negated by the actions on tariffs.”

Trump has already imposed 25 percent tariffs on imported steel and aluminum and targeted $50 billion worth of Chinese goods for increased levies. He’s also threatening to boost penalties on up to $500 billion of Chinese imports and take “tremendous retribution” against European automakers.

Business leaders have reacted with almost universal hostility. The Washington Post filed a report from Columbus, Indiana — the hometown of Vice President Mike Pence as well as the headquarters of Cummins Inc., a manufacturer of large industrial equipment that depends heavily on the export market.

“I’m very worried,” said Tom Lineberger, the company’s chief executive. That’s because higher tariffs hurt Cummins in two ways: by raising the cost of raw materials like steel and by inviting retaliation against its finished products sold abroad.

Harold Force, who runs a construction company in Columbus that employs 250 people, is already coping with rising prices on many items he buys and has canceled plans to expand his workforce.

“I think this is much bigger than people think,” he told the Post. “When it started, it was a shock. I thought, ‘Is this really happening?’ Then one of our biggest projects in recent times was canceled because of steel prices. It’s damaging in so any ways. Tariffs have put blood in the water.”

There’s blood in the water in farm country, as well, since American agricultural exports amounted to $140 billion last year. And China’s threats to retaliate against U.S. soybean growers has “caused the market to collapse in recent months,” reports The New York Times.

“That really makes farmers nervous. We’ve all got bills to pay,” said Ron Moore, an Illinois farmer who heads the American Soybean Association.

The blowback has been so fierce Trump offered a $12 billion bailout package for farmers. But Republicans like Sen. Rand Paul immediately denounced it. “If tariffs punish farmers, the answer is not welfare for farmers,” said Paul. “The answer is to remove tariffs.”

Perhaps most alarming is Trump’s threat to impose tariffs on foreign-made cars and car parts. The president displays a towering ignorance about how the international market really works, with American companies depending heavily on foreign sources for key components of every car they make.

A study by the Center for Automotive Research estimates that Trump’s proposed tariffs would add from $980 to $4,400 to the price of each American-made vehicle — a devastating development for carmakers and car buyers alike. As Republican Sen. Lamar Alexander of Tennessee, a big auto-producing state, put it, “These tariffs are dangerous. They are going to cost us jobs and lower our family incomes.”

Dangerous. Stupid. Reckless. And that’s just what Republicans are calling Trump’s trade policies.

He won’t listen. He thinks he knows better. But obviously he doesn’t. And the “blood in the water” continues to spread.

Steve and Cokie Roberts can be contacted at stevecokie@gmail.com.