Bush did not leave office with the debt at 5T. In fact, they had to add another digit to the symbolic debt ticker under his watch, as he pushed the debt through the 10 trillion mark. Again, depending on how you run the books, he ran the debt up anywhere from 4.7T to 8T, largely with a republican congress 6/8 of the time.
You're right about needing to focus on the present guy in office, and reel in his spending. I couldn't agree more. I just don't want us to gloss over the republican's recent record, so we won't mistakenly think that by re-electing the likes of Bush/Cheney, it will make the spending like a drunk sailor go away. We've all seen the chart posted here several times about which administrations run up the big bills. Obama might finally bring the democrats to that party, that has mostly been republican up till now.