At risk senate seats

I'm trying to figure out how many Senate seats, and which ones, will switch from Republican to Democratic in November 2016. At present, 54 Senator caucus with the Republicans, and 46 caucus with the Democrats (two of those are Independant). We should be shooting for a good majority of 61, just to be safe. That means fifteen Republicans have to go, to result in a 39 to 61 mix. To get a simple majority, only five Republicans have to be replaced, to produce a 49 to 51 mix. So, we should be working for replacing fifteen but hoping to replace at least five. A perusal of The Internet…