Democrats like to blame Washington’s mushrooming deficits on the Trump tax cuts, but new data from the Treasury Department this week shine a light on the biggest culprit: runaway spending.

Federal outlays for the first 10 months of this fiscal year hit $3.7 trillion, a record sum, even after adjusting for inflation.

Indeed, the highest previous inflation-adjusted cash splurge over that period, $3.6 trillion, came in 2009 — when massive funds were channeled to the Troubled Asset Relief Program and the Obama stimulus package in an effort to pull the nation out of the Great Recession.

Meanwhile, the fiscal 2019 deficit, year-to-date, is pushing $900 billion, on its way toward topping the $1 trillion mark by year’s end. Yet Dems can’t fairly blame the tax cuts for the monster gap: Over that 10-month period, revenues shot up a healthy 3.4% — i.e., faster than GDP — thanks to a strong economy.

So there’s no shortage of cash coming in; it’s just that even that revenue can’t keep pace with the 8% jump in spending.

Not that either Republicans or Democrats care: Last month, President Trump and Congress agreed to lift budget caps by $320 billion over the next two years.

“Congress and both parties have become big spenders,” sighed David M. McIntosh of the Club for Growth when the deal was struck. “They’re no longer concerned” about budget deficits or the debt.

They should be: By borrowing more to spend more, Washington is paving the way for a dangerous spiral, as higher interest payments mean even more spending. How long do they think that can last?