She said the mistake was discovered yesterday during the canvass.
She stressed it was not a case of votes being found.
"I’m thankful that this error was caught early in the process and during the canvass," Nickolaus said. "The purpose of the canvass is to catch these kinds of errors."
The wild swing in Prosser's favor immediately raised concerns among Dems, who pointed out Nickolaus is a former staffer for the Assembly Republican Caucus who was granted immunity in the investigation into allegations of illegal campaign activities on state time.
Ramona Kitzinger, the Democratic member of the county board of canvass, defended the process. She agreed with Nickolaus that the board "went over everything and made sure that all the numbers jived up, and they did."
"I'm the Democratic vice chair of Waukesha County, so I'm not going to stand here and tell you something that's not true," Kitzinger said.