NSA consequences on security clearance?

[question asker]

If one were to go through the NSA process for hiring and fail the polygraph whether innocent of allegations or not, and not admit anything during the interrogation would this affect future security clearances? More specifically a DOD secret security clearance? I know the SF86 asks nothing about past polygraphs, only clearance experiences. I've seen similar discussions, but none came to a clear conclusion. Also does the polygraph take place before the BI?

Thank you in advance

[question asker]

I also read in some previous forum threads that the polygraph alone cannot be used to disqualify you a clearance, is this true?

https://antipolygraph.org/forum/index.php?topic=4457.msg33784#msg33784