Which sets of Senators were facing election that year? As a rule, only approximately a third. It would be nice to see if they were correlated to the group "swit

Which sets of Senators were facing election that year? As a rule, only approximately a third. It would be nice to see if they were correlated to the group "switching" sides. Which party controlled the Senate that year? It would be interesting to see if switching is correlated to party control. For instance, I see the Republicans controlled the Senate in the 108th (2003-2004).