Like other Tweeters, U.S. senators and representatives who use the Twitter micro-messaging service choose whose feeds they wish to follow; these attention preferences are depicted below by arcs connecting followers to followees. Members of Congress and associated entities (the Hispanic Caucus and the Prayer Caucus, for example) are arrayed and colored on our diagram according to the partisan lean of the congressional people and entities they choose to follow — going from most Democratic in blue on the left, to most Republican-leaning in red on the right.
The arcs are colored according to the partisan lean of the member or entity whose messages are being followed.
The bar graph at bottom shows the number and partisanship of members following and followed by each congressional person or entity; it also shows the broad range of engagement and bipartisanship involved in the congressional Twitter network.
Republicans outnumber Democrats on Twitter by roughly 2 to 1, and, among other things, this diagram clearly reflects the surprising dominance of the Grand Old Party in its use of this new medium.
It also shows a tendency that is perhaps less surprising: Republicans in Congress, it seems, are interested largely in what other Republicans have to say — even when what they're saying can't run longer than 140 characters.
Data sources: TweetCongress.org and the Twitter application programming interface.