Eric Holder campaigns for Rebecca Dallet as GOP questions her ability to hear controversial cases on Wisconsin Supreme Court

Former U.S. Attorney General Eric Holder came to Milwaukee Thursday to implore liberal activists to turn out the vote for Supreme Court candidate Rebecca Dallet and fight election maps that favor Republicans.

Holder, who served in President Barack Obama's administration, said the Milwaukee County judge is "the clear choice" in the race and lauded her for being "tough, fair and compassionate."

Meanwhile, Republicans stepped up their attacks against Dallet, questioning her ability to hear certain types of cases and criticizing her for a San Francisco fundraiser.

In the April 3 election, Dallet faces Sauk County Circuit Judge Michael Screnock, who has won the backing of Republicans.

The winner will replace Justice Michael Gableman, who is not seeking a second term. Gableman is part of the court's 5-2 conservative majority.

Holder heads the National Democratic Redistricting Committee, which is spending $140,000 on digital ads backing Dallet. He said his group will be monitoring the race over the next two weeks and said it was a "distinct possibility" that it would be spending more in support of Dallet.

Last month, Holder's group sued GOP Gov. Scott Walker to try to force him to hold elections to fill two vacant seats in the state Legislature. Holder chided Walker for keeping the seats vacant while also calling for a special legislative session on school safety.

"He considers himself a conservative, I'd say he's regressive," Holder said of Walker. "He's doing whatever he can to maintain power, surrounding himself with people who share those views."

Heading to the fall elections, Holder said Democrats need to be more disciplined and focused to match Republicans.

"We have to be ready to, you know, not do anything inappropriate, not do anything improper, certainly not do anything unlawful," he said. "But to the extent that they want to have a fight, let's do it. You want to rumble, let's rumble. You want to have a knife fight, we're gonna do it."

J. Mac Davis, a former Republican state senator and former Waukesha County judge, questioned Dallet's ability to hear an array of cases, including ones brought by Holder's group and those involving firearms.

Dallet in turn has said Screnock should not be able to hear cases involving the state's largest business lobbying group, Wisconsin Manufacturers & Commerce, because it has spent hundreds of thousands of dollars backing him.

Davis said that by drawing a firm line about when judges must step aside in cases, Dallet was setting a higher bar for herself and opening herself to criticism for being hypocritical.

"If you're going to pose for holy pictures, you've got to expect people to pick at you," said Davis, who is backing Screnock.

Meanwhile, Screnock's campaign consultant, Sean Lansing, criticized Dallet for holding a fundraiser in San Francisco next week hosted by Democrats in the California Legislature.

"In today’s example of @judgedallet saying one thing and doing another: campaigns on 'Wisconsin values,' goes to San Francisco less than 3 weeks before the election to raise $ for her campaign. #DoubleTalkDallet," Lansing wrote in a post on Twitter.

Dallet is also getting help from Democratic U.S. Sen. Tammy Baldwin, whose operation is conducting 64 door-knocking and phone-banking events in 38 counties this weekend to turn out voters for Dallet and Baldwin. It's a dry run for Baldwin's get-out-the-vote efforts for her fall re-election bid.

Dallet did not appear at Holder's Milwaukee stop and was not planning on attending one he has slated for Friday in Madison.

The lawsuit over special elections is expected to be resolved before the winner of next month's Supreme Court election is seated in August. But Holder's group could bring other litigation that could eventually make its way to the Supreme Court.

Dallet has decried as too weak the state Supreme Court's ethics rule that allows judges and justices to remain on cases involving those who bankrolled efforts to elect them. She said spending by Holder's group might be so large as to force her off a case involving the group.

RELATED: Wisconsin high court candidates Rebecca Dallet and Michael Screnock divided over guns, NRA

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Holder said Dallet wouldn't have to recuse herself "from the question generally. If we were bringing a case, ourselves, as an organization I think at that point she'd have to seriously think about recusing herself."

Davis said he did not believe spending alone was enough to push justices off cases, but said some of Dallet's statements might. Those comments — such as ones supporting gun control — could amount to an "implicit promise" about how she would rule that would require her to step aside, Davis said.

Davis said supporters of gun rights would have concerns about Dallet's ability to be impartial given a pledge she took against the National Rifle Association.

"Everybody who goes to court, they want to win, but they also want fairness," Davis said.

The NRA has endorsed Screnock, but Davis said he did not think Screnock would be barred from hearing gun cases because he has not stated his personal views on firearms.

Dallet has said she believes limits on guns can be constitutional and that belief does not limit her ability to hear cases involving firearms.