As a senior recruiter, I recall being bemused by candidates who were personable and friendly toward me as the interviewer, yet were dismissive or cold with junior team members or support staff they encountered.
When you are involved in an interview process, remember that everyone you encounter can have an influence on whether you secure the role. From the assistant who arranges your appointment to the receptionist who greets you on arrival, all these members of the organisation are forming an impression of you.
Hiring managers often like to know what other people think of a candidate, especially if it is small company or if there are several comparable candidates available. Recruiters will also discuss their impression with other team members if they need a second opinion.
Being charming and affable will also show an employer that you are happy to be there and genuinely want the job. Remember to be courteous, smile, and make good eye contact with all those you encounter.