John McCain entered tonight’s debate needing to halt Barack Obama’s momentum and fundamentally change the dynamic of the race.Not only did he fail to achieve this goal, McCain dug himself an even deeper hole.Undecided voters watching the debate felt McCain gave a decidedly un-presidential performance, appearing rude, negative, and easily flustered – a stark contrast to Barack Obama’s cool, commanding presence.Obama was seen as the clear victor in the debate, and a group that was much more disposed to support McCain at the outset instead shifted decisively toward Obama (42 to 20 percent) after viewing the debate.