Among the many peculiarities of the 2016 election, this one ranks high: The presumptive Republican nominee has signaled that he would spend more, and make the deficit larger, than President Obama.

You read that correctly.

Republicans have devoted years to attacking Mr. Obama as a debt-expanding spendthrift, even as the deficit has declined by more than two-thirds as a share of the economy since 2009. Yet primary voters sidetracked those concerns in backing Donald J. Trump as their candidate to succeed him.

The combined effect that Mr. Trump’s spending and tax-cut commitments would have on the size of government and the volume of red ink confounds veterans of Republican policy debates.

“There is no way,” said Douglas Holtz-Eakin, an economic adviser to President George W. Bush, “to describe him as a fiscal conservative.”