In the Driver’s Seat

What does the idiom “in the driver’s seat” mean?

Definition: In a dominant position, in control

Example: The New England Patriots are in the driver’s seat, with a 12-point lead going into the fourth quarter.

Note: You’d think this could be used for only one person—only one person can sit in the seat of a car. But usages for a group, as in the example above, are common.