Depends on how "badly" you perform and how quickly you improve. If the only thing the admissions board has to look at is a failing CFA, it could color their view and, in no event, would you be able to earn an appointment until you pass. If you do ok (passing each event and not doing poorly in any), but not exceptionally well, and you are otherwise well-qualified, it may not hurt you at all.
In any event, for a lot of reasons, you want to show up at NASS in good shape and do well on the CFA there. It's only Dec (as of tomorrow) and NASS isn't until June. That gives you 6+ months to get in shape -- plenty of time. Start committing yourself now to be successful in the long run.