That's the debatable part. Given the absolutely massive power imbalance, can it be consensual?
From my perspective, I think it's important to take Ms. Lewinsky's opinion and consider it to not be sexual assault, she's had about 30 years of reflection on it and where she landed is consensual.
But I can understand, given the power imbalance and how that has been used historically to force others into a sexual relationship, how it can be viewed as sexual assault.