I have no idea why Obama doesn't point this out. So I am going to do it for him. Since President Roosevelt (1945) no Democratic President has added to the National debt - except Obama. Of the 14 Trillion National Debt 12 Trillion of it was added by Republicans! While it did go up slightly under some Democrats, that was because of interest on the debt that was added by Republicans. It actually went down under Democrats Roosevelt, Truman, Kennedy, Johnson, Carter and Clinton. It also went down under Republican Presidents Eisenhower and Nixon. But under Republicans Ford, Reagan, Bush 1, and Bush 2, it went up. It went up HUGELY under Reagan and the two Bushes.
Clinton not only balanced the budget, he had a surplus, that he wanted to put towards paying off the National Debt. In fact under his plan for the next ten years the National Debt would have been paid off completely by now. But then came George W Bush who had "A better Idea". Not only did he not use the surplus generated by Clinton towards the debt he actually cut the top tax rate and borrowed even more money to pay for it. He also started two wars, and borrowed to pay for those too. By the time he left office the National Debt was doubled! And Obama was saddled not only with that huge debt but the interest on it, plus the continuing costs of the tax cut and the two wars started by his predecessor.
Along with the refusal by the Republicans to raise the top tax rate on the rich, plug loopholes to huge Corporations paying NO taxes, or even to allow the Bush tax cuts to expire, the situation was impossible. With no way to raise revenue and nowhere to cut spending except trifling cuts to things like NPR, EPA, etc Obama was forced to put his sacred cows on the block - Soc Sec and Medicare.
Just allowing the Bush cuts on the rich to expire, the budget would have been close to balancing again. At 39% under Clinton the budget was in a surplus situation. Cut to 35% by Bush with no plan to pay for the cut - except to borrow to pay for it - there was no hope.
So in spite of virtually the entire National Debt being added by the Republicans, the Republicans have managed to convince the public that the whole amount is the fault of the Obama administration!