After a close contest, Barack Obama claimed victory over Mitt Romney on his Twitter feed shortly after the major networks called the election in his favor.

One of Obama's tweets was signed "-bo," an indication the president himself wrote it, not his staff.

A tweet showing the reelected First Couple embracing became the most retweeted tweet of all time, with more than 630,000 retweets and counting. The same message and picture were posted on Obama's Facebook page. At 3.2 million "likes" and counting, it has become Facebook's most "liked" photo ever. 

Shortly after his concession speech, Mitt Romney posted this "Thank you" image on his Facebook page, which garnered a little more than half a million "likes." As of 12:45 p.m. on Nov. 7, Romney had not updated his Twitter feed.

Twitter confirmed that Election Day was the most tweeted-about political event ever in the U.S., with more than 32 million tweets in 24 hours.

Much of the social media activity on Election Day -- and throughout the campaign -- was dominated by Obama supporters. Among other potential reasons for this dominance, social sites tend to skew liberal. A recent study by the Pew Research Center’s Internet & American Life Project found that 79% of liberals use social networking sites. In contrast, only 63% of conservatives do the same. 

On Facebook, the top mentioned terms on Election Day were "Obama," "Vote/Voted," and "Romney." On Election Night, the top three mentioned terms were "Obama," "4 more years / 4 years," and "President / President Obama."

Democratic women also had a big night. Come January, more women will serve in the Senate than at any time in history. Two contests of note: Democrat Elizabeth Warren unseated Massachusetts Republican Sen. Scott Brown, and in Wisconsin, Rep. Tammy Baldwin, a Democrat, defeated four-time governor Tommy Thompson. 

Republicans may have lost the presidential race and had a weak showing in Senate races but performed better in House races. House Speaker John Boehner, a Republican, and Rep. Michele Bachmann, who was re-elected to her seat, both tweeted out messages. 

Donald Trump, an outspoken critic of Obama, was quite vocal on Twitter.

Voters also took to Twitter to voice either their excitement or dismay. Many used the hashtag #P2, in support of Obama, or #tcot, in support of Romney.