What's moving markets today: Live updates - CNN

We're entering a new phase of President Donald Trump's trade wars. As political economist Greg Valliere wrote this morning in a note, "These tariffs break new ground -- they're political, a punishment to Mexico for not stopping the surge of immigrants from Central America."

Republicans haven't pushed back on Trump's trade strategy. Until now. This is from Iowa Senator Charles Grassley: "Trade policy and border security are separate issues. This is a misuse of presidential tariff authority." Retaliation from Mexico, of course, could hurt Iowa's farmers and pork producers.

Meanwhile, the fear around the world this morning is that tariffs will hurt both countries. Weakening the Mexican economy, of course, could have the opposite effect on illegal immigration than Trump wants. But the president is clearly devoted to his tariffs-as-punishment strategy. "This finally could awaken the slumbering U.S. Congress," Valliere wrote.

I've said for some time that markets have been resilient in the face of what could be a years-long trade war with China, potential tariffs down the road on European and Japanese cars, and now new tensions with Mexico. But the past month has been a different story. For investors, May has been a reckoning.

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