Undecided voters: Romney ‘stepped up’

>> media. getting reaction to a debate isn't a morning after thing anymore. it's a real time thing about the talk about the event is still going on tonight. that part of our story from nbc's john yang .

>> the right answer is to say how do we make the private sector more efficient.

>> reporter: even before the candidates finished talking, another debate was raging online. the twitter world exploded. a conservative journalist, an absolutely one sided debate. big, big win for romney . bill maher . i can't believe i'm saying this, but obama looks like he does need a telepromter. analyst stu rothenberg . what happened to obama? the president didn't seem prepared. it continued on the air waves.

>> i don't know what he was doing out there. he had his head down, enduring the debate.

>> romney supporters set brated.

>> this was from start to finish, particularly measured against fears and expectation.

>> reporter: after enduring weeks of headlines about gaffes, romney woke up to read he had been declared the debate winner. the obama campaign struggled to explain.

>> so, you're happy with his demeanor and energy level tonight?

>> what i'm happy with is the path he wants to lead this country on.

>> reporter: even while cheering the president today, his supporters seemed puzzled by his debate performance.

>> i didn't know quite what was going on as far as maybe he's dealing with some crisis in the middle east .

>> reporter: and battleground states like colorado and ohio, undecided voters nbc gathered to watch the debate say they saw something new.

>> governor romney just sort of stepped up his game in terms of bringing something new to this campaign.

>> it did change the way i thought about him. i liked him better.

>> reporter: it was the most heavily tweeted in history. even big bird was a hot topic. this went viral. if mitt romney wins, this is what i'll be forced to do. this tidal wave of real time commentary on social media is just another uncontrollable factor that campaigns struggle to deal with as they try to get their messages out.

>> john yang sampling the reaction in chicago and elsewhere. peter