million are fans of Mitt Romney. "If you're on Team Obama, let him know," says one post on the president's page shared more than 159,000 times.
US President Barack Obama (R) greets Republican presidential candidate Mitt Romney (L) following the first presidential debate at Magness Arena at the University of Denver in Denver, Colorado. (AFP Photo)
First Lady Michelle Obama, meanwhile, has 8.5 million Facebook fans -- ahead of Romney's wife Ann (381,000). But in the VP race, Joe Biden trails far behind his Republican rival Paul Ryan.
Twitter: @BarackObama has more than 20.8 million followers. Present on the social network since March 2007, his team often posts comments on his behalf. His own tweets are followed by the initials 'bo.' Obama's account is the 6th most followed in the world, according to Twopcharts, which tracks the most influential active Twitter users. But the president still trails far behind the world's most followed 'Tweep' -- Lady Gaga -- and her 30 million followers.
@MittRomney arrived on Twitter two years after his rival and lags behind, with more than 1.4 million followers. His is the 925th most followed account in the world. @JoeBiden, meanwhile, once again trails behind @PaulRyanVP.
Google+: Barack Obama has more than 2.2 million fans on Google's social network, almost twice as many as Romney's nearly 978,000 followers.
YouTube: Barack Obama has just under 240,000 followers of his YouTube channel, which integrates campaign ads and filmed messages of support for the Obama team. Beyonce, for instance, appears in a video praising the First Lady.
Mitt Romney, meanwhile, has a little less than 23,700 fans. His page also includes campaign ads and other videos, including one depicting his "love story" with wife Ann.
Pinterest: The latest social media phenomenon -- which allows users to post and share photos put together by theme -- is the more "intimate" of all the networks. On his page (more than 34,600 followers), Obama's team has posted light-hearted snaps, such as photos of the president stroking his dog Bo under the heading "Pet Lovers for Obama."
Romney is on Pinterest with a mere 1,700 followers, but his wife Ann has drawn a following of more than 12,400. She has posted photos of herself cooking M&M cookies with her grandchildren or of a meatloaf cake -- "one of Mitt's favorites." Michelle Obama is also on Pinterest, with just under 43,000 followers. Her page includes gardening snaps taken around the White House.
Instagram: On this photo-sharing social network, some 1.5 million people follow Barack Obama's campaign shots. Far behind, Mitt Romney is "followed" by 30 times less people.