I don't know enough about Broaddrick's claim to pass judgment, but from what I've seen of her on TV, she seems "credible" for what that is worth.
On the other hand, I watched every minute of Dr. Ford's testimony and she never seemed "credible" to me. She wasn't "incredible" in the sense that she came across as demented, but, to me at least, she came across as acting.
I freely admit that as a conservative I didn't want to find her credible, but all I can say about that was that I was prepared to find her believable. Take that with a grain of salt as you will.
I watched her testimony with my 26 year old daughter-in-law who was a victim of a sexual assault (she actually reported it to the police) and she didn't find her credible either. Being a victim doesn't make one a truth-detector, but she viewed the testimony from a perspective that I don't have.