and I know you are talking about flips

but if we are talking about longshots, we need to add McCaskill (barring her heartfelt apology to black voters) and Heitkamp (barring overwhelming rage over being lied to by Trump from the (former) oilfield workers in the Bakken who are living on public assistance).

Looking at AL-2017 (Jones-D),TN-2018 (Mackler-D/Berke-D),TX-2018 (O'Rourke-D),and UT-2018 (Wilson-D/Matheson-D/McAdams-D).
TN-2018(Mackler-D/Berke-D) is winnable for Democrats. The last time a Democrat won a TN US Senate Race was in 1990 (Gore-D was re-elected to a 2nd term.) The last time a Democrat came close to winning a TN US Senate Race was in 2006 (Ford-D narrowly lost to Corker-R). Mackler-D and/or Berke-D have more crossover appeal than Ford-D. The likely 2018 Republican nominee will be more extreme and controversial than Corker-R.