The ballooning deficit defies a historic trend: Typically, the budget deficit shrinks when unemployment is low. But it is increasing despite the longest economic expansion on record and the lowest jobless rate in 50 years.

It also underscores the degree to which Republicans in Washington — who championed fiscal responsibility under President Barack Obama, a Democrat — have largely abandoned that goal. While lawmakers continue to talk about the need to reduce the deficit, it is no longer the kind of animating issue that ushered the Tea Party into power.

Mr. Trump has shown little inclination to prioritize deficit reduction, and has instead considered policies that would add to the debt. The president has mused in recent days about reducing the taxes that investors pay on capital gains, a move that is estimated to add $100 billion to deficits over the next decade. He has also talked about cutting payroll taxes, which could reduce revenues by $75 billion a year for every percentage point cut in payroll tax rates.

Mr. Trump backed away from both ideas in comments to reporters on Wednesday, though it is unclear if the new deficit figures played any role in that reversal.

The president also wants to make permanent many of the temporary individual tax cuts contained in the 2017 law, which are scheduled to expire in 2025. The budget office forecast assumes those cuts expire and tax revenues rise; if they do not, future deficit projections would be even larger.

Mr. Trump’s indifference to deficits has shattered his campaign promise not only to balance the budget, but also to pay off the entire national debt. And it has left his fellow Republicans, who pushed through deficit-reduction measures under Mr. Obama when the economy was still fragile, in a bind. Congressional Republicans have largely gone along with Mr. Trump’s moves to add more debt, even as they insist they will return to shrinking the deficit if Mr. Trump wins a second term in office.

The deficit has now risen four consecutive years, and is on track to rise for the next four. Such a streak would break the record for longest run of deficit increases in recorded American history — five years, from 1939 to 1943 — according to the Peter G. Peterson Foundation, an organization that advocates deficit reduction.