The rhetoric has changed too, with Republicans no longer talking about the deficit and the debt in the heated, worried way they once did. During the 2016 GOP debates, the fiscal situation came up far less often than it did in 2012, and with far less urgency too. The Senate Budget Committee held no dedicated hearings on the debt, the deficit, fiscal stability, or balanced budgets in 2017, unlike in many years past. And, as a great FiveThirtyEight analysis has found, mentions of the deficit during congressional proceedings peaked at more than 8,000 in 2011 and fell to just more than 1,500 by 2015. For their part, administration officials refer to it infrequently, and often with little sense of outrage or concern. “The president is very much concerned about the rate of increase of the debt,” Steven Mnuchin, the Treasury secretary, said at a hearing of the Senate Banking Committee this week. “Over time, we need to figure out where we can have government savings to deal with the deficit.”

So what happened? How did the same Republicans who balked at a stimulus to get the country out of a recession rubber-stamp a bigger stimulus to fuel the best economy since the 1990s? How are the same Republicans who helped to construct an automatic mechanism to slash spending now lifting caps, spending more, and leaving entitlement programs untouched?

I asked both Democratic and Republican aides those questions, and got mostly shrugs. In some sense, President Trump is just doing what Presidents George W. Bush and Ronald Reagan did before him, aided by Republicans in Congress. Both swore to balance the budget or to bring down the debt. Both signed legislation that increased deficits instead, primarily through tax cuts and increased military spending.

Many Democrats, for their part, now believe that Republicans exploited their sincere concern over the long-term fiscal situation to score short-term political points—with some Democrats privately vowing not to worry about paying for things once they are back in power. “Republicans never really cared about the budget deficit. It was always a political tactic. With their own tax cut, they said, ‘Go ahead and finance it with massive deficit spending,’” Jared Bernstein, an Obama economic adviser, told me. Democrats struggled to ensure everything they did was paid for, while, Bernstein argues, “Republican fiscal irresponsibility has enabled them to provide all kinds of goodies to their donor base.”

But Washington’s understanding of the economic situation has changed, too, as Bernstein admits. It now seems clear that the degree of deficit panic whipped up in the post-crisis years overestimated the risk of a bond-market reaction, overstated the risk of the government crowding out private investment, and underestimated the capacity of the United States government to run deficits and build up debts—as well as overestimating how much voters ever really cared about the deficit. “If you go around yelling about pressure on interest rates and public borrowing crowding out private, you don’t have a lot to point to in terms of data,” Bernstein told me. “You have virtually nothing in terms of data. That’s not just here. That’s in Japan, other advanced economies as well.”