Americans flocked to social networks all day to post photographic proof they had cast their ballots, with 22 percent of voters using Twitter, Facebook and others to announce who they voted or planned to vote for, one study found.
"I'm checking in because polls will start closing in this election in just a few hours, and I need you to vote," President Barack Obama said on social news site Reddit -- one of several social media pushes for votes by the incumbent.
Reddit is a widely-used website that allows users to rank posted information according to whether they like it or not. Obama conducted a much-publicized online chat with the public on the site in August.
"I voted for you. Best of luck tonight Mr. President," one netizen named "WordSlinger81" wrote under Obama's post.
As the evening progressed, the Democratic incumbent continued to push Americans to vote even as polls shut in one state after the other.
On Twitter, his team posted messages directed at followers in those states still voting, reminding them to stay in line even if polling stations officially closed.
"Nevada, pass it on: Polls close at 7pm PT. You can vote as long as you're in line before then," his team posted, using the widely-used hashtag #StayInLine.
Republican challenger Mitt Romney, meanwhile, appealed to his 1.7 million Twitter followers in a post retweeted 3,215 times.
"With your help, we will turn our country around and get America back on the path to prosperity. Please vote today," he said late Tuesday.
Campaigns, celebrities and others have used social networks extensively to try to persuade people to vote and even beat the record 2008 turnout, when two-thirds of US voters cast a ballot.
On Tuesday, photos abounded on Twitter of people proudly sporting their "I voted" badges and some also posted shots of their ballot papers -- which is illegal in some states.
"Just cast my vote & my grandpa would be so proud!", @She_Weezy2012 tweeted, posting a picture of an "I Voted" sticker on her grey jumper, complete with the #ivoted hashtag, which was being used by hundreds of Twitter users.
Wearing aviator sunglasses and a black cap, singer Lenny Kravitz also waded into the fray, sticking his "I voted today!" badge on his finger in a photo on his Twitter account.
The social network announced mid-evening that over 11 million poll-related tweets were fired off during the day, possibly breaking the record held by the first presidential debate of the most tweeted event in US political history.
Facebook itself posted messages at the top of people's news feeds on Tuesday showing users which friends were voting in the election and urging them to do the same by clicking an "I'm a voter" button.
On a separate page, a real-time map of the United States lit up in various areas as soon as a person clicked the button, with a counter clocking up the millions of Facebook voters (http://www.facebookstories.com/vote).
Two-thirds of these were women, according to Facebook statistics.
In a study, the Pew Research Center found that 22 percent of respondents in a representative sample of 1,011 adults said they had let people know who they voted for or planned to vote for on social networking sites.
Nearly one-third of voters had been encouraged to vote for Obama or Romney via posts on social media, while one-fifth had tried to convince others to cast their ballot on social networks.
Some enthusiastic netizens put up photos voting with their children during the day -- an initiative backed by First Lady Michelle Obama, who has encouraged Americans to take their kids to the polls so they get an idea of the workings of democracy.
Others took to Twitter to point out irregularities. Romney campaign spokesman Ryan Williams posted a photo of a polling station in Philadelphia that had a huge painting of Obama on its wall complete with the word "hope."
Electioneering is not allowed at polling places in some states, and he later updated followers with a picture of the same Obama mural covered up by several pieces of paper, saying it was still "not good enough."
Many also checked in on the location-based social network Foursquare to pinpoint exactly where they cast their ballot, and tens of thousands of photos were posted on photo-sharing platform Instagram with the hashtag #ivoted.