Milwaukee Mayor Tom Barrett announced on March 30 that he would enter the Democratic primary in the effort to recall Gov. Scott Walker. Shortly after entering the race, Barrett asked his Democratic opponents to pledge to keep negative ads out of the primary campaign. Days later, AFSCME, which has endorsed Kathleen Falk in the primary, released an attack ad against Barrett.

Pundits had speculated since the beginning of the recall petition drive last November that Barrett, who lost the race for governor to Walker in November 2010, would enter the race for governor. However, Barrett held off his announcement until the day the GAB certified the recall petitions, March 30, which also happened to be the Friday before the Tuesday, April 3 election day when the Milwaukee Mayor is elected. Barrett, who was running for re-election, easily beat a token candidate on April 3, so he will remain mayor while running for Governor.

Shortly after entering the race, Barrett asked his Democratic opponents to pledge to keep negative ads out of the primary campaign. Under Barrett’s pledge, if a candidate or outside group ran an ad attacking a Democratic opponent, that candidate would have to make a contribution of half the value of the ad to a charity of the targeted candidate’s choice. Barrett’s top competitor, Kathleen Falk, declined to sign the petition.

A day later, Wisconsin’s largest public employees union, the American Federation of State, County and Municipal Employees (AFSCME), launched an attack ad against Barrett that suggests he supported Walker’s changes to collective bargaining.

AFSCME has endorsed Falk in the primary in part because she promised the unions she would veto any state budget that doesn’t restore collective bargaining rights. Barrett refused to make such a pledge.

The other Democrats running in the primary are Secretary of State Doug La Follette and state Sen. Kathleen Vinehout.