Moody’s Ratings service waddled in Friday to state the obvious, which is that the U.S. is on an unsustainable debt trajectory. We’d like to know where Moody’s was when the Biden Administration was spending at record levels, but there’s still a warning here for the Republicans now in charge in Washington.

Moody’s downgraded U.S. debt to a notch below its top rating, citing chronic budget deficits and rising debt-service costs. The rating agency lagged behind S&P Global Ratings and Fitch, which downgraded the U.S. in 2011 and 2023, respectively. Moody’s may have been late because it believes in the Keynesian model that government spending lifts economic growth.

Markets on Monday reacted poorly to the downgrade, as well as comments by Treasury Secretary Scott Bessent that there may be more bad tariff news coming. He said the April 2 “reciprocal” tariffs could return for some countries if they don’t agree to President Trump’s supposedly generous terms. The 30-year Treasury bond yield hit 5% for the first time since autumn 2023, before falling back, and the 10-year appears to be settling near 4.5%.

Moody’s is no oracle, but its downgrade is a moment to explain America’s real deficit and debt issue. The problem is spending, which neither political party wants to restrain. More revenue from faster economic growth would help, but supply-side growth policies have ebbing political support, even in the GOP.