Sure you can. It is important to change the main driver up to 48 hours before the scheduled pick-up time. This type of change is not possible at the car rental desk, and almost always incur additional charges. Even though it might look like an easy change, the main driver amendment is often considered as a main change, and may result in rebooking against the current applicable rate.
Such amendment is also necessary if you realize that the main driver does not have their own credit card for the deposit.