In a sometimes-heated final debate Thursday night, Milwaukee Mayor Tom Barrett (D) drilled in on the ongoing criminal investigation of some of Wisconsin Gov. Scott Walker's (R) former aides.

Walker and Barrett have run hard-hitting ads questioning each other's honesty in recent days — Barrett's targeted the probe, while Walker's ads have questioned whether his police department has doctored statistics on violent crime. Both topics were the focus of the debate, and showed that in a race that started out as a referendum on labor rights, the final days will be fought on more personal territory.

"I have a police department that arrests felons," Barrett said at one point, according to the Milwaukee Journal-Sentinel. "He has a practice of hiring them."

Thirteen former Walker aides from his time as Milwaukee County executive have been granted immunity in the case in exchange for their cooperation, including Walker's former spokeswoman at the department, whose name was added to the list this week.

Walker criticized Barrett for how his police department has handled crime statistics. Barrett has touted a drop in violent crime, but a Journal-Sentinel piece showed much of that drop might have derived from massaged statistics.

The two will face off in the recall election on Tuesday. Walker has led narrowly in most nonpartisan polls, but Barrett hopes that a visit Friday from former President Bill Clinton will help stir up enthusiasm for his campaign.