WASHINGTON — In 2009, almost every Republican in Congress opposed a $787 billion stimulus plan in the midst of an economic crisis because they said it would cause a dangerous increase in the federal debt.
Nine years later, during one of the longest economic expansions in American history, almost every Republican in Congress — including Mr. McConnell, now the majority leader — supports a tax plan that is projected to cause an even larger increase in the federal debt.
Republicans got to that extraordinary point by a tangled path. First they argued that the tax cuts would stimulate the economy enough to pay for themselves, only to be confronted on Thursday with a report that said the cuts would add $1 trillion to the deficit over a decade. That bad news led to last-minute convulsions and a frantic search for more revenue.
But in the end, the political imperative to pass what would be the only major piece of legislation of President Trump’s first year, along with a near-religious Republican belief in tax cuts, overrode their previous concerns about fiscal prudence.
All but one Republican senator, Bob Corker of Tennessee, voted for the bill early Saturday.
The House and the Senate still have to reach a final agreement on the details, and Mr. Trump has to sign his name, but the Republican Party now stands on the verge of driving up the national debt after spending much of the last decade promising rectitude and criticizing Democrats for profligacy.
The legislation reads “as if it were developed for a country whose debt problems have been solved, when in reality debt is the highest it has ever been other than around World War II,” declared the co-chairmen of a bipartisan commission created in 2010 to propose measures for reducing the debt.