As Maclean’s Paul Wells reports, Donald Trump’s rising dissatisfaction with America’s trade deals with Canada may have hit a tipping point Monday afternoon. Wells reports that Trump is said to have seen a segment on Fox featuring a distressed Wisconsin dairy farmer who, should nothing change between now and May 1, could be forced to dump much of the milk his farm produces, as he can no longer sell it to Canada. As Wells writes, The Fox News story egged the President on in his growing suspicion that Canada, far from being cuddly and Ivanka-friendly, is actually a marauding border-squatting trade succubus.” And so, a trade war—now involving a softwood lumber tariff—may erupt.

Opening a segment on Fox Business yesterday, reporter Jeff Flock knelt next to some dairy cows in Fox Lake, Wisc., and laid the blame squarely on America’s neighbour to the north.

“They thought that President Trump was going to start the trade war. Well, it looks like Canada may have fired the first shot,” he said.

The reason dairy matters? It all rests on a high-protein concentrate called “ultrafiltered milk” that’s used in making cheese and yogurt. Because of its recent introduction, ultrafiltered milk hasn’t been subject to a negotiated tariff under NAFTA, and so it could be imported into Canada cheaply. In response to this, Canada’s dairy industry recently introduced a new pricing class of milk, which was meant to incentivize Canadian farms to produce unfiltered milk, therefore cutting into U.S. imports (and those of places like Australia and New Zealand). For those countries, the new class system in Canada appears unfair.

Why does May 1 matter? And why is Wisconsin so important? May 1 is when a major U.S. producer, Grasslands Dairy Products Inc., plans to cancel its contracts with 75 Wisconsin farms if nothing changes.

It’s worth noting that in this Fox segment, the dairy farmer Flock interviews doesn’t necessarily blame Canada for what might happen to his milk, and subsequently his farm. “We need immediate help,” Tony Senn said. “I don’t believe that looking at Canada to correct this problem at this time is going to be the answer.” That jives with what some other Wisconsin farmers have said recently. When the CBC talked to dairy farmers, they suggested blaming Canada for their situation is misguided. “Suddenly, everyone was pointing the finger at Canada, but that’s not really what’s going on. We have overproduction here in Wisconsin, and we really need to address that here at home,” Sarah Lloyd, a dairy farmer near Madison, told the network last week, in the wake of Trump’s initial anti-Canadian dairy salvo.