In the second presidential debate on Tuesday night at Hofstra University in Long Island, New York, a reinvigorated President Obama took the fight to Mitt Romney. The president appeared far more energetic than in the first presidential debate, which was widely deemed a dominant victory for Romney. Democrats have called on Obama to challenge Romney more aggressively, and he did so early, exclaiming, "It's not true!" when the GOP candidate claimed that Obama essentially followed Romney's proposals for saving the auto industry. Here, some reactions from the Twitterverse:

Hey everybody, Obama woke up. — daveweigel (@daveweigel) October 17, 2012

Obama speaking about 100% more vigorously than in Denver. #debates — Roger Simon (@politicoroger) October 17, 2012

Obama's back on. I recognize this guy. Energy; focus; ability to relate. thebea.st/V7xk8A — Andrew Sullivan (@sullydish) October 17, 2012

Obama goes for the throat. Works. — david carr (@carr2n) October 17, 2012

Obama was so feisty that it drew some counterpunches from Romney, and the two men squared off face to face in a tense moment on the debate floor. More from Twitter, and watch the video below:

RT @davidplotz: Wowza. Are they going to brawl? — Slate (@Slate) October 17, 2012

Romney: "You'll get your chance in a moment, I'm still speaking." Yeow. — Molly Ball (@mollyesque) October 17, 2012

This isn't a town hall, its a mob watching a street fight. — Garrett Haake (@GarrettNBCNews) October 17, 2012

Watch the exchange: