Nearly all of the national debt is the result of policies signed into law by Republican presidents.
The calculation behind this number is shown on this page.
I’ve explained my own calculations previously, coming to the same conclusion. Although it looks like that post may have been eaten in the switch to a new web server.
Short answer:
$1 trillion in debt prior to reagan
$0 debt added from clinton policies
roughly $200 billion from obama policies
Even if you wrongly claim all debt prior to reagan was (D) policy, that means (D)’s are at 1.2 trillion of the 18 trillion in debt, or 6.67% of the total debt.
Leaving (R)’s total at a minimum of 93%+.