U.S. Budget Watch, a project of the bipartisan Committee for a Responsible Federal Budget, released a report Thursday indicating debt would increase most under policies supported by former Sen. Rick Santorum of Pennsylvania and former House Speaker Newt Gingrich.
Both propose big tax cuts without spending reductions to cover the lost revenue, the report said.
Under Santorum's proposed policies, the national debt would climb by about $4.5 trillion by 2021 and under Gingrich's proposed policies by $7 trillion during the same time span.
Romney's proposed policies would add $2.6 trillion to the debt by 2021, Budget Watch said.
Of the four major Republican candidates, only Texas Rep. Ron Paul's proposed policies would cut future borrowing, by about $2 trillion, the report said.
"As we enter the thick of the campaign season, no one can ignore the debt issue," said Maya MacGuineas, president of the Committee for a Responsible Federal Budget, which supports debt-reduction efforts. "This report is designed to inform the public on the fiscal policies put forward by each of the Republican candidates and stimulate debate on this crucial topic."
The Washington Post said the report is the first independent attempt to measure the impact of GOP candidates' proposed policies on the nation's $15.4 trillion debt.