Potential husband doesn't want me to wear the hijab.

If married, do I have to obey him?

No, you do not have to obey him. Prophet said there is no obedience to the creation in disobedience to the creator and not wearing hijab is an act of disobedience. It is a sin. It is obligatory for Muslim women to wear hijab as Allah has commanded in the Quran, and therefore their husbands have no right to tell them to not wear hijab.

And so, if you were to marry him, you do not need to obey him. But, you may want to reconsider whether marrying somebody who doesn't want you to wear hijab is a good idea. Because what other things, Islamically, will they not want you to do? And how much pressure will they put upon you, and your children, if you have daughters to openly sin.