Barack Obama brought his sophisticated social media campaign to an emotional climax, proclaiming his victory on Twitter and Facebook just as TV networks were breaking the news.
Obama overcame the burden of a slow economic recovery and high unemployment to beat Republican foe Mitt Romney after a relentless get-out-the-vote push on Twitter, Facebook, Reddit and other platforms.
"This happened because of you. Thank you," he tweeted to his 22 million followers just minutes after the first US network called his victory, in an indication of the importance he attached to social networks in his campaign.
"Four more years," he said straight afterwards, posting a photo of himself hugging First Lady Michelle Obama as other TV networks followed suit and, one-by-one, announced his re-election as 44th President of the United States.
The post was his most re-tweeted -- 472,000 shares in three hours -- according to Twitter's politics account @gov. It was also the most popular ever, topping a message from singer Justin Bieber, website BuzzFeed said.
The same picture of a happy, serene-looking Obama hugging his wife appeared on the president's Facebook account -- and was shared tens of thousands of times by some of his 32 million fans.
"We did it, we voted for you, now please dear president Obama do what you said you will do, make us proud: Education, Health Care, Green Energy for USA!," Angela De Jesus said under the photo, one of 80,700 comments.
Social networks have emerged as key tools in the months-long US presidential campaign, with both Obama and Romney staging major pushes on these popular platforms to draw in supporters and get them to go out and vote.
But while Romney has increased his presence hugely on social media compared to 2008 Republican presidential candidate John McCain, Obama is seen as having retained the upper hand from his successful online campaign four years ago.
Already in January, Obama's campaign manager Jim Messina had hinted at a huge social media campaign in an interview with Newsweek.
"Our efforts on the ground and on technology will make 2008 look prehistoric," he was quoted as saying.
And even as election day drew to a nail-biting close late Tuesday afternoon, Obama made a surprise appearance on social news website Reddit, where he made a last-ditch plea for more votes.
"I'm checking in because polls will start closing in this election in just a few hours, and I need you to vote," he said on the popular site, which allows users to rank posted information according to whether they like it or not.
As the evening progressed, the Democratic incumbent continued to push voters to the polls on social media, even as polls shut in one state after the other.
His campaign team fired messages to those Twitter followers located in states that were still voting, reminding them to stay in line even if polling stations had officially closed.
Romney, by comparison, sent a general tweet out early evening to his 1.8 million followers asking them to vote, but stayed silent thereafter.
"With your help, we will turn our country around and get America back on the path to prosperity. Please vote today," it read.
According to Twitter, the election has become the most tweeted about event in US political history, with some 31 million poll-related posts fired out throughout day.
When networks called the victory, Twitter went into manic overdrive, with election-related tweets rising to an average of 327,452 a minute.
Netizens flocked to social networks to congratulate the re-elected President, as did British Prime Minister David Cameron.
"Warm congratulations to my friend @BarackObama. Look forward to continuing to work together," he tweeted, during a visit to the Middle East.