states are indexed by when terms end:  1987, 89, 91:

87 and 89:  AZ, CA, CT, FL, HI, IN, MD, MO, NV, NY, ND, OH, PA, UT, VT, WA, WI
87 and 91:  AL, AK, AR, CO, GA, ID, IL, IA, KS, KY, LA, NH, NC, OK, OR, SC, SD
89 and 91:  DE, ME, MA, MI, MN, MS, MT, NE, NJ, NM, RI, TN, TX, VA, WV, WY