United States of Amoeba by Kenneth Cukier

Everyone knows that American politics has become more polarised over the past quarter-century. In this motion infographic, the effect is shown visually—with troves of data, statistics and “force-directed graphing”, a technique to depict positions based on attraction-and-repulsion models adapted from physics.
The network maps here look at the degree to which senators vote the same way over the course of a quarter-century. Each node is a senator. Links represent instances when senators have voted similarly on substantive legislation on at least 100 occasions during the same congressional session. Their intensity is the degree to which they vote the same. Their placement is determined algorithmically, based on their co-operation with other legislators—which has the effect of pushing more bipartisan ones to the centre.
About 25 years ago, American policymaking looked like a tightly bound ball with lots of meshing in the middle, as senators regularly crossed the aisle to get things done. Over time the two sides have split apart, like an amoeba dividing, separating into distinct spheres that share little common voting. Though America’s political polarisation has become a fact of life, it has never been seen so graphically with data: as a diseased brain, with few neural pathways between the two hemispheres.