Congressman and Senators can nominate anyone they choose. They are allowed to reach out to one another, to see who each other is giving their nominations to. They can choose to spread the wealth, and not double up on nominations, or all can choose to nominate the same individual. Some will only give an individual a nomination to one service academy, others will nominate an individual to multiple service academies. Some Congressman and Senators provide the academies with their preferred/primary nomination, but most choose to let the academies decide who is the best candidate. It is best to apply to all sources of nominations that you can, prepare for any interviews, be polite and professional, do the best you can and hope for the best. The waiting is the hardest part.