MADISON, Wis. -- A day after opponents to Wisconsin Gov. Scott Walker filed more than 1 million petitions to recall him from office, a prominent Democrat jumped into the race against him.

Kathleen Falk, the former elected executive of Madison-based Dane County, said Wednesday she is a candidate for the Democratic nomination to oppose Walker. She joins state Sen. Tim Cullen, a moderate Democrat who has said he is also in the race.

"One million Wisconsinites signed recall petitions in an unprecedented and inspiring show of solidarity and determination," Falk said in a statement. "Things are not working here and we must, we can and we will do better."

The petition filing on Tuesday virtually assures that Walker, a Republican beginning only his second year in office, will face a recall election, probably in the summer. The state's Government Accountability Board must verify that enough petitions were filed to force an election. That number is only 540,208, which gives recall supporters confidence that the certification of the recall election is just a matter of time.

Cullen, of Janesville, said on Tuesday that he remains in the race. He has had a lower profile during the recall effort than Falk, who has appeared at numerous rallies and traveled the state to support the petition-gathering drive.

Other prominent Democrats have been known to be considering running, including former U.S. Rep. David Obey and Milwaukee Mayor Tom Barrett, who lost to Walker in November of 2010. State Sen. Jon Erpenbach, who was the voice of Democratic opponents to Walker during last winter's battle over collective bargaining rights, said he is considering running.

Cullen said this week that his main goal will be to "heal the state" of the emotional divisions that have arisen under Walker and the Republican-controlled Legislature. He said under Walker, there was little consultation with opponents. Erbenbach said the Democratic contender must be more than the anti-Walker candidate, but must promote a positive vision for the state's future.

The state's Democratic Party chairman, Mike Tate, said he expects there will be several Democratic contenders, requiring a primary to decide which one will face Walker.

Falk was the first woman to be elected executive of Dane County and was re-elected three times. She lost two statewide runs for office -- for Governor in 2002 and for Attorney General in 2006.

"I will make different choices than Scott Walker," Falk's statement read. "The people of Wisconsin have done a brave thing: demanded change."

Walker's campaign group issued a statement saying Falk is the "nominee hand-picked by big-government public employee and union bosses." The statement noted that Falk "has already lost two statewide elections, failing to earn the trust of Wisconsin voters."

Another leader who has emerged during the recall effort, Mahlon Mitchell, a fire department lieutenant in Madison and president of the Professional Firefighters of Wisconsin, said Tuesday he is considering running for lieutenant governor. The recall also applies to Lt. Gov. Rebecca Kleefisch, who will likely have to defend her office in a recall election as well.