GOP Presidents Have Been the Worst Contributors to the Federal Debt
In terms of total increase in "federal debt to GDP" under U.S. presidents in the post-World War II era, Republican presidents during their terms have contributed far more to the debt load of the nation than Democrats.
Gerald Ford, Ronald Reagan, George H.W. Bush, and George W. Bush all added to the federal debt significantly on a percent of GDP basis. On the Democratic side, President Obama -- who inherited the worst financial crisis in this era from his predecessor -- also ranks high in terms of contributing to the federal debt as a percentage of GDP.
Who reduced debt as a percentage of GDP the most?

While absolute levels of debt may have been growing through much of this period (though not all), what really matters is what percentage of GDP that debt represents. Most U.S. presidents have been able to keep the debt to GDP ratio declining -- but in the very modern era, since 1980, only Bill Clinton has succeeded in massively decreasing America's federal debt to GDP levels.

When looking at the charts this way, it is fascinating to see what a stand-out the Bill Clinton presidency was in balancing the budget and achieving revenue surpluses.
These data sets were assembled by a close collaborator and credit expert Richard Vague as part of a larger history of debt project that he and I are working on.
As the debates on who is responsible for the levels of federal debt continue to play out in the next 10 days before the election and the 66 days before the US hits a fiscal cliff, remember that the worst contributors to America's debt load were mostly GOP presidents -- with the single exception of Obama, who had a global economic tsunami crashing in on the White House and nation when he took the helm.