While presidents bear some responsibility for the debt and deficit spending, the major responsibility lies with Congress.
As the following graph shows (courtesy of Wikipedia), it isn’t the control of the White House so much as it is control of the House and Senate:
Notice that when purple (split control) the graph generally increases or flattens, when blue (Democrat controlled) it generally increases, sometimes sharply, and when red (Republican controlled) the curve tends to flatten or decrease. This trend persists, even today, as the latest purple region is starting to flatten, although the jury is still out on the effect that the TEA party influence will have after 2012. I suspect that their influence will make the purple curve look more like the trends for the full Republican (red) control, but Øbama’s possible reelection might offset that.
Some things never change…