For years, Republican lawmakers lamented the soaring national debt, pressing for spending cuts and clinging to the mantle of fiscal responsibility. But last week, Senate Republicans hammered out a deal to allow for as much as $1.5 trillion in tax cuts, betting that supercharged growth will make up for lost revenue, a potentially dubious prospect. The tax plan outlined Wednesday by the White House and Republican leaders in the House and Senate could cost more than $2 trillion over the next decade, according to a preliminary estimate by the Committee for a Responsible Federal Budget, a nonpartisan advocacy group.

This month, the majority of Republicans in the House and the Senate voted to raise the debt limit without doing anything to rein in spending.

Republican lawmakers are pushing to increase military spending by tens of billions of dollars, topping even Mr. Trump’s request for a beefed-up military. Democrats are sharing in the fiscal intemperance, lining up behind a “Medicare for all” proposal despite having no definitive plan for how to pay for universal, government-provided health coverage.

And as Congress mulls large tax cuts, the tabs for Hurricanes Harvey, Irma and Maria keep rising.

When Mr. Bush took office and pushed for a big tax cut, the fiscal outlook was strong. The Congressional Budget Office in 2001 was projecting $5.6 trillion in budget surpluses over 10 years.

Now, the budget office forecasts that deficits will total $10.1 trillion over the next decade. The deficit is expected to top $1 trillion a year in 2022 and keep growing from there. Federal debt held by the public is at the highest level since shortly after World War II, at 77 percent of the gross domestic product.