Courtesy of TPM Reader AD, a little nugget from 1999 in WaPo (emphasis added)...

Christian politicians and evangelical leaders commonly follow an unspoken rule not to meet behind closed doors with women staff members or travel alone with them. The Rev. Billy Graham, for example, has famously refused to be alone in a room with any woman except his wife since he married her in the 1940s.

Rep. Steve Largent (R-Okla.), a Christian conservative, insists a male staff member is present whenever he meets with a woman, his spokesman said. John Ensign, who is running for senate in Nevada will not be alone in a car with a woman