The current map of US Senate seats up for grabs
Red -- Democratic incumbent
Blue - Republican incumbent
Independents are placed as they caucus.
A lighter shade involves an open seat due to a retiring incumbent.
An asterisk indicates an appointed incumbent. (We have none of those as of January 22, 2015).
To suggest how the map can change, imagine this unlikely scenario:
President Obama appoints Senator Debbie Stabenow (D-MI) to a cabinet post (yeah, sure -- and weaken his Senate minority). The Republican Governor of Michigan Republican-dominated state legislature then appoints by its vote Representative Tim Walberg (R-MI) (also unlikely because such creates an open House seat in 2016 that the Republican Party may need, and Walberg is such a marginal politician that he could never be elected in a statewide race in Michigan) to the vacated seat. One of two things will happen to make a distinction on the map:
Either the newly-appointed US Senator Tim Walberg acts as if he wants to to run for re-election:
...or or commits to not do so:
I told you that this is a very unlikely scenario; it is only an illustration so that I can show an appointed seat and a Republican who intends not to run for re-election.
I suggest the first map for updates.
