Go to your state purchase and bid contracts. You can find the Patrol Car specifications. A lot of states are specifying AWD Patrol cars. That could be the reason that many state police cars are Explorers, Durangos, and Tahoes. Local agencies will piggyback off of the state specifications. Any legitimate auto dealership is welcome to bid. The low bidder usually wins out.
The Explorer, Durango, and Tahoe are about the only vehicles that offer what is considered a true police package AFAIK.
I think that the Expedition and Suburban also can be ordered with police packages as well.
There are a few other vehicles, such as the Equinox and the Traverse, offer a heavy duty package, that some jurisdictions may buy for non patrol duties. They are not rated for patrol duties, however.
Chargers were the last sedan option for police work.
Without a doubt, they were also the low bid option for many departments.
I saw that one of the adjoining counties just bought 4 Explorers. Cost upfitted was just shy of 90K each.