Both Helms' and Sam Nunn's names have come up, but both were elected to the Senate in 1972, taking office in January of 1973. The VVAW Phoenix Project was debated and voted on in November of 1971.
It's possible that the list wasn't exclusively Senators, and Nunn was a Congressman from 1969 to 1973, but Helms was a radio and TV exec for a dozen years before going to the Senate.
