Red and Blue are More Divided than in the Past

Source: The Washington Post

Look at the horizontal axis that measures political ideology. In the 1950s, the Republicans (red) were more like the Democrats (blue) than they are today,. In the 1950s there was some considerable overlap in ideology between middle of the road Democrats and Republicans, which no longer exists.

Look at the vertical axis that measures how frequently the Representative votes with his/her party. In the 1950s quite a few Democrats and Republicans voted with the other party a significant portion  of the time; now block voting characterizes members of both parties, although a few Democrats on the right wing of the party still vote occasionally with the Republicans.

Both the red dots and the blue dots cluster more closely in the last Congress than they did in the 84th Congress. Republicans, as a party, have moved more to the right. More Democrats represent progressive ideology, and the right wing of the Democratic party is weaker and its Representatives in the House less conservative. (Remember the realignment of the conservative South during the Civil Rights movement, when it stopped electing Democrats and switched to electing Republicans.)

In the 1950s, either party could pass a bill by making it somewhat more acceptable to the centrist members of the other party. Now the Republicans drive bills through the Republican-majority House of Representatives that get shot down in the Democrat-majority Senate.

The explanation of gridlock made visual.