• Trump's
• However, the auto industry might take the tariffs in stride and eat the higher commodity costs.

On Thursday, the Trump administration announced a tariff on imported steel and aluminum, signaling a willingness to start a trade war so that that the President could keep a campaign promise.

The response from US steel- and aluminum makers was swift and positive, although it's worth noting that the aluminum industry in the country has been in steady retreat since 1980.

Automakers who use a lot of steel and aluminum in their vehicles were either quiet or diplomatic, even as slower February sales compared to a year ago and the Trump announcement send the entire sector's stock prices into decline.

Trying to understand Trump tariffs

But during the presidential campaign and into his first year in office, Trump has shown little understanding of the global auto industry. So it shouldn't be a surprise that, although he needs Detroit to invest and hire in critical 2020 election states such as Michigan and Ohio, he's doing exactly the opposite of what the industry needs — and maybe even raising the price on that new pickup a voter has been planning to spend his tax-cut money on.