BR & BDR Election Process
If a DR and BDR already exist on a network, any new comers will accept them regardless of their own Router ID/Priority.
The first router on the network becomes the DR. The next will become with BDR. Other routers will accept these 2 routes as DR and BDR, and form adjacencies with them.
OSPF doesn’t allow pre-empting of a DR when a new comer has a better Router ID/Priority. This allows for better network stability since a router with a higher priority, oscillating from up to down, will not affect the router already selected as the DR