President Donald Trump’s pledge to send every American adult a $5,000 check if Republicans hold Congress in November carries a price tag that economists say has no clear funding source — and would land on a federal balance sheet already strained by a nearly $2 trillion annual deficit.

Kent Smetters, faculty director of the Penn Wharton Budget Model and one of the country’s most respected fiscal economists, estimated the plan would cost about $1.35 trillion if paid to the full population of American adults, in a statement emailed to Fortune. Factor in Vice President JD Vance’s suggestion that the checks wouldn’t go to “the wealthy” — using a household income cap of $400,000, which Smetters called “a reasonable guess” since no threshold has been specified — and he calculated that the cost would still come in around $1.15 trillion.

Either figure would be financed the same way most of Washington’s recent spending has been: borrowed.

A promise without a payment plan

Trump made the pledge Wednesday night during a nearly two-hour speech at the Republican Party’s midterm convention, held in Dallas. “If the Republicans win the House of Representatives and the United States Senate, I will issue a dividend to every adult citizen in the United States of America for $5,000,” Trump told the crowd, dubbing it the “Trump Dividend.”