There are only a few things that can happen and not many variables to contend with, so it is easy to build a probability table for the outcomes regarding Mike Castle.
Then we can quibble over the probability of each outcome, but the short version is there is only a slim chance that Mike Castle will be in elected office after the next election. A 20% chance to be exact.
Castle can chose one of three options. He can run for his House seat. He can run for the Senate seat, or he could retire. The other variables effecting the outcome are the choices faced by the Democrats. They only have two. They can either run an “A List” person against Castle or a “Non-A List” person.
So these are the possible combinations:
1) Castle Runs for his House Seat against an “A List” Dem = 30% prob.
2) Castle Runs for his House Seat against a “Non-A List” Dem = 20% prob.
3) Castle Runs for the Senate seat against an “A List” Dem = 10% prob.
4) Castle Runs for the Senate seat against a “Non-A List” Dem = 0% prob.
5) Castle retires for public life = 40% prob.
Note that option 4 has a zero percent chance of happening since the Dems are not going to give away a Senate seat. Of the remaining possible outcomes, there is only one that I would consider a “bad” outcome and that is number 2.
That is the only scenario in which Castle might win re-election. The question now is, how do we hedge against item number 2 from coming to pass?