Poll workers operate in close proximity to one another and work under the supervision of the Chief Inspector. They do not work in secret. There is never a single poll worker working at a polling place. There are also often observers in the polling place on Election Day.
Per Wis. Stat. §6.79(1m), “The municipal clerk may elect to maintain the information on the poll list manually or electronically. If the clerk elects to maintain the list electronically, an election official at each election ward shall be in charge of and shall maintain the poll list. The system employed to maintain the list electronically is subject to the approval of the commission. If the clerk elects to maintain the information manually, 2 election officials at each election ward shall be in charge of and shall maintain 2 separate poll lists.”
A large part of maintaining two separate lists is implementing a redundant check to ensure electors are being recorded appropriately and that the voter numbers match throughout the day. Badger Books do this on a larger scale with the voter transactions taking place on every device visible to all other Badger Books in the polling place. Whatever a poll worker does on one Badger Book is visible to any other poll worker on any other Badger Book. As each poll worker has unique credentials for the Badger Book application, all voter transactions, including checking in voters or processing Election Day Registrations, can be tied back to the poll worker who completed that transaction. So, Badger Books have more people looking at the poll book, not less.
Ballots are handled separately from the Badger Books and must be initialed by two election inspectors to become live. For that reason, a single corrupt poll worker couldn’t check off voters and vote ballots on behalf of electors who did not vote.