You need both candidate and thesis to be good for a PhD. Your examiners need to ask you – the candidate – about both in the viva.
What’s your thesis’ contribution? How did you do it? And what can you do well?
They’re looking for clear confirmation that your thesis has a significant, original contribution, that you did the work and that you’re a good researcher.
If that sounds like a lot, remember:
No candidate, no thesis.
No thesis, no candidate.