The Senate has voted 92 times in current session, 60 percent of which relate to the all-nighter the chamber held last Friday (known as the "vote-a-rama") in the process of passing its first budget in four years. After voting on 70 of the 572 amendments that senators proposed to the legislation, Senate Concurrent Resolution 8, the Democrats pieced together exactly 50 votes to pass it.
All four Democrats who voted against the measure—Mark Pryor of Arkansas, Kay Hagan of North Carolina, Mark Begich of Alaska and Max Baucus of Montana—are among those up for re-election in 2014 and represent states that elected Mitt Romney in November. This represents one of the clearest fault lines so far in the otherwise highly cohesive Democratic caucus. When Yahoo News debuted its Senate Social Network a week ago, when the chamber had voted 37 times, there were 22 Democrats who had voted alike every single time. That is no longer the case.
That interactive is updated below. Note that, to maintain any connection between the parties, the default threshold for connecting any two senators has been reduced to 65 percent—that is, any two senators are connected if they have voted together 65 percent of the time.
If you drag the slider to the right, you will see that the Democrats continue to maintain a stronger hold on party unity than the Republicans. But the seams are fraying, and the budget will not be the last time in the 113th Congress that vulnerable Democrats have to make hard choices about when to leave the fold.