If you do not have a TS, and do not get through the
poly, then NSA will not direct the DSS to start the TS
background investigation.  If you already have a TS,
and do not get through the poly, I know that DSS does
not look at the poly results, but looks at any derogatory
volunteered information.  The TS is granted by DSS and
the SCI by NSA.  If you have a TS, and get through the
poly, but do not get through NSA adjudication, I don't
believe that it would affect the TS, unless there are
major issues that the DSS does not know about. If you
do not get through the NSA process, then trying to get
a DoD clearance may be more difficult.  You just have to
weigh, for yourself, if getting the NSA SCI is worth
risking getting a DoD/DSS clearance.  Fun, hugh ?