The tweet is signed "-bo," the campaign's way of signaling the president wrote it himself.

Networks declared the race for Obama following his projected win in Ohio, a key battleground state.

Obama's Twitter feed went on to tweet "four more years," along with a smiley photo of the president and first lady. That tweet quickly accumulated not only the most re-tweets of any tweet from Obama's account, it also jumped within half an hour to the most shared tweet in Twitter history, passing the previous record winner by Justin Bieber.

Bieber's most popular tweet had more than 200,000 re-tweets. Obama's tweet had more than 300,000 less than an hour after posting. 

Twitter also reported a huge spike in Twitter conversation following the announcement that Obama has been re-elected, with 327,453 tweets per minute at 11:19 p.m. 

The election had already become the most tweeted political event in history earlier in the evening, with more than 20 million election-related tweets sent by 10 p.m.

Updated at 12:09 a.m.