I just checked AIPAC’s web site. For their recent pro-Israel letter, signed by 87 Senators, 6 of 57 Democrats, 6 of 41 Republicans, and 1 of 2 Independents did not sign. The non-signatories are as follows:
Sessions (R-AL)
Dodd (D-CT)
Lugar (R-IN)
Bunning (R-KY)
Kerry (D-MA)
Gregg (R-NH)
Bingaman (D-NM)
Coburn (R-OK)
Alexander (R-TN)
Leahy (D-VT)
Sanders (I-VT)
Webb (D-VA)
Goodwin (D-WV)
Goodwin may not have been in the Senate at the time the signatures were being collected.