Republican presidential candidate Mitt Romney and U.S. President Barack Obama shake hands following the second presidential debate at Hofstra University in Hempstead, New York, on Tuesday, October 16, moderated by CNN's Candy Crowley. See the best photos of the first presidential debate.
President Obama and first lady Michelle Obama embrace after the debate.
U.S. President Barack Obama and Republican presidential candidate Mitt Romney point fingers at each other.
U.S. President Barack Obama and Republican presidential candidate Mitt Romney speak over each other.
President Obama and Republican presidential nominee Romney point the finger at each other.
CNN's Candy Crowley moderates the second presidential debate between President Obama and Republican presidential candidate Mitt Romney.
President Obama and Romney clash during the debate.
Romney and President Obama interrupt each other during the debate.
Republican presidential nominee Mitt Romney and U.S. President Barack Obama debate.
U.S. President Barack Obama and Republican presidential candidate Mitt Romney both speak at the same time.
Republican presidential nominee Mitt Romney and President Obama go head to head.
Romney gestures to make a point as President Obama looks on.
U.S. President Barack Obama and Republican presidential candidate Mitt Romney square off.
U.S. President Barack Obama listens to Republican presidential candidate Mitt Romney.
President Obama promotes his policies as Mitt Romney listens.
Republican presidential candidate Mitt Romney addresses a question as President Obama listens.
President Obama awaits his turn to speak.
U.S. President Barack Obama and Republican presidential nominee Mitt Romney greet the audience.
Republican presidential candidate Mitt Romney and U.S. President Barack Obama greet each other on stage.
U.S. President Barack Obama and Republican presidential nominee Mitt Romney shake hands.6.
President Obama and Republican presidential candidate Romney shake hands before the start of the debate.
Moderator Candy Crowley of CNN speaks to the audience prior to the start of a town hall-style presidential debate.
Ann Romney, wife of Republican presidential candidate Mitt Romney, speaks with members of the audience before the start of the second presidential debate at Hofstra University in Hempstead, New York, on Tuesday, October 16.
First lady Michelle Obama awaits the start of the second presidential debate.
Republican presidential candidate Mitt Romney and his wife Ann await the start of the second presidential debate in a holding room.
The audience gathers in the stands prior to the start of the presidential debate on Tuesday.
Co-chairs Frank Fahrenkopf, left, and Mike McCurry of the Commission on Presidential Debates speak in the lead up to the town hall-style debate.
Audience members take photographs while they wait for the debate to begin.
Members of the audience have taken their seats.
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STORY HIGHLIGHTS
- Republicans and Democrats work together on one thing: presidential debates
- Danke schoen to a German University of Maryland student for presidential debates
- Abraham Lincoln, zingers and pigeon soup have something in common
- Only two debates have impacted the outcome of an election
(CNN) -- Presidential debates haven't been around forever. A woman hasn't moderated a presidential debate in 20 years. A German immigrant is to thank for election season's October verbal battles. And Abraham Lincoln might have pioneered debate zingers. Don't believe us? Read on.
Fast facts
• Howard K. Smith of CBS News moderated the first modern presidential debate in 1960.
• In 1992, Carole Simpson of ABC became the first woman to moderate a debate. She was also the first African-American to do so.

President Barack Obama and Republican presidential candidate Mitt Romney finish their debate in Denver on Wednesday, October 3. View behind-the-scene photos of debate preparations.
Romney stands with his wife, Ann, and family following the first presidential debate.
President Obama kisses first lady Michelle Obama after the debate Wednesday. It took place on their 20th wedding anniversary.
Jim Leher of PBS moderates the 90-minute debate on Wednesday. It was the candidates' first time debating face to face.
Obama defended his record and challenged his rival's proposals.
Romney was more aggressive Wednesday in criticizing Obama's vision.
People watch the debate at Galapagos Art Space in Brooklyn, New York.
The event was expected to draw the candidates' largest nationwide audience to date.
Romney answers a question from the moderator.
Obama argues his view. Both candidates said the other's proposals won't work.
Michelle Obama listens to the debate.
Romney said Obama has failed to bring down high unemployment and get the economy surging again.
Obama reacts to Romney's remarks on Wednesday.
Obama listens during the debate in Denver.
Romney, who has been unable to catch the president in most polls to date, sought to generate enthusiasm for a change in the White House.
Romney's shadow is projected beneath text from the Declaration of Independence at the University of Denver's Magness Arena.
The first of three presidential debates focused on domestic issues: the economy, health care and the role of government.
Obama and Mitt Romney clashed over the economy on Wednesday.
Romney speaks during Wednesday night's debate. The candidate called for a new economic path.
Obama called for "economic patriotism" and said Romney's plan of tax cuts for the rich failed before.
Romney and Obama wave to the crowd at the start of the presidential debate.
Obama greets Romney on Wednesday.
The candidates meet on stage less than five weeks before Election Day.
Obama and Romney shake hands Wednesday night.
The presidential race has been dominated so far by negative advertising as both camps try to frame the election to their advantage.
Leher takes the stage Wednesday. It's his 12th time moderating a presidential debate.
Michelle Obama points to Lehrer before the start of the debate.
Ann Romney and first lady Michelle Obama hug on Wednesday.
The candidates wives were in attendance for the most highly anticipated campaign event to date.
Michelle Obama sits with White House Senior Advisor Valerie Jarrett, right.
Rapper Will.i.am, left, speaks with Jarrett before the debate on Wednesday. View behind-the-scenes photos of debate preparations.
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HIDE CAPTION
Photos: The first presidential debate
• Jim Lehrer of PBS moderated his 11th presidential debate on October 3, 2012. Those and the one vice presidential debate he moderated earns him the nod for the most debates moderated.
• The Commission on Presidential Debates, founded in 1987, is a nonprofit organization that produces the presidential and vice presidential debates. It is funded by private donations from foundations and corporations, but is controlled by the Republican and Democratic parties.
Gloves off at second presidential debate
The first modern presidential debate
• The first televised debate was in October 1960 when then-Sen. John F. Kennedy and then-Vice President Richard Nixon went head to head in the debate watched by 66.4 million people. Sixty-one percent of voters watched it on television. Those who listened on radio thought the debate was a tie or that Nixon won. But for the 61%, Kennedy's charismatic performance in contrast to Nixon's sallow appearance handed him the debate. Three more debates were televised in the 1960 contest and aired on all three networks: ABC, NBC and CBS. It wasn't until the 1976 election that another general presidential debate was held.
• The 1960 debate is also the first presidential debate -- all debates before then were in primaries or in congressional races. In 1940, Republican presidential nominee Wendell Willkie challenged President Franklin D. Roosevelt to a debate but the incumbent dismissed it as a publicity stunt. Willkie later refused a debate challenge by Socialist party candidate Norman Thomas.
Where they stand: The candidates and issues
• An attempt by Friedrich Kahn, a University of Maryland student, in 1956 could have displaced the 1960 debate's place in history. Kahn, an enterprising German immigrant, wanted presidential candidates to answer student questions in a debate format. To set it up, he reached out to national media outlets and to the former first lady Eleanor Roosevelt to set up a presidential debate between Dwight D. Eisenhower and Adlai Stevenson. Roosevelt said the debate could energize the student population and threw her clout behind Kahn's initiative.
Not wanting to serve as a political platform shortly after its university president used his position as a jumping off point for his gubernatorial run, the school banned political speeches on campus before the debate. The decision forced Kahn to cancel.
• Some precursors to the modern presidential debate exist. The earliest of note was between then-Illinois congressmen Abraham Lincoln and Stephen Douglas in 1858, who debated seven times in their run for the state's U.S. Senate seat.
Transcript: Second presidential debate
Reagan: 'Are you better off?'
Bush checks the time
Al Gore sighs while Bush speaks
Crowley as moderator: 'Career highlight'
What moments made history?
• Homeopathic soup: Lincoln might have pioneered debate zingers. In the 1858 debates, Lincoln famously called a Douglas policy on slavery in the territories, "as thin as the homeopathic soup that was made by boiling the shadow of a pigeon that had starved to death." Zing.
• "Are you better off now...?": President Reagan first posed the question to the American public at the end of a presidential debate in 1980. It was a gamble, but it paid off, his Democratic opponent, President Jimmy Carter, served for one term. Republicans co-opted the phrase at the 2012 Republican National Convention, as they tried to paint President Barack Obama as a Carter-like president.
America's voters: CNN Poll of polls
• The sighs have it: In the 2000 election, then-Vice President Al Gore unloaded several heavy sighs while opponent then-Texas Gov. George W. Bush was answering questions. While focus groups thought Gore had performed better, the sigh heard round the world, parodied over and over, enforced the perception of Gore as a know-it-all. Not to blame Gore's heavy breathing, but he later lost the election.
Will 2012 debates make history? Yes, TBD and not sure yet.
• Yes: This year's debate marks the first time in 20 years that a woman has moderated a presidential debate: CNN's Candy Crowley. Including Crowley, there have been eight female moderators since 1960.
Another nugget about women and the debates? Only two female candidates have ever taken part in a general election debate. Both Geraldine Ferraro in 1984 and Sarah Palin in 2008 were candidates for vice president.
• TBD: There have been no defining zingers and gaffes thus far, although Joe Biden tried to recycle Lloyd Bentsen's "You, sir, are no Jack Kennedy," delivered to Dan Quayle in the 1988 vice presidential debate. As Paul Ryan was talking about Kennedy cutting taxes, Biden retorted, "So now you're Jack Kennedy?"
• Not sure yet: Only two debates -- 1960 and 2000 -- were game-changers, a Gallup Survey found. But a CNN poll immediately after President Barack Obama and Mitt Romney's first debate earlier this month showed that 67% of debate watchers said Romney won -- the first time any presidential candidate has topped 60% since the question was first asked in 1984.
A snapshot of the nation: CNN Electoral Map
CNN's Amy Roberts, Keating Holland, Alan Silverleib and Robert Yoon contributed to this report