Finally, Obama has taken a page from Biden's debate book

When Romney went on with twisted facts, Obama this time chimed in with a short line, "It's not true". Nowadays, people just have super short memory. So it's important to insert doubt into audience's mind, when your opponent is telling half truth. You will have easier time to clarify that afterwards.

The debate is still going on, but Obama's performance comparing to last time, is already day and night.