MADISON, Wis. (AP) – The Republican candidate for Wisconsin governor, Scott Walker, refused to say Tuesday whether he favors a ban on embryonic stem cell research – even though he previously told an anti-abortion group he does.

Embryonic stem cell research was pioneered at the University of Wisconsin-Madison, and millions of dollars is spent on it each year in the state. In 2006, Democratic Gov. Jim Doyle made support for the research a focus of his successful campaign, and Walker’s Democratic opponent, Milwaukee Mayor Tom Barrett, has tried to do the same.

Polls show Barrett trailing Walker.

During a Tuesday campaign stop in Madison, Walker said he would direct state money to stem cell research that doesn’t use cells obtained from embryos.

However, many researchers believe embryonic stem cells hold the most promise because they can morph into any type of cell and potentially be used to cure diseases like Parkinson’s, diabetes and spinal cord injuries.

When repeatedly asked whether he would support an outright ban on embryonic stem cell research, Walker avoided a direct answer.

“I do not support destroying a human embryo,” he said. “I’m going to put the money behind adult stem cell, not behind embryonic.”

But Matt Sande, political action committee director for Pro-Life Wisconsin, said Walker previously told his group he supports a ban. That’s one reason Walker received a 100 percent rating from the group, Sande said.

While Walker has been careful to avoid talking about an embryonic stem cell research ban on the campaign trail, Barrett has been running an ad in which the mother of a child with juvenile diabetes says Walker wants to ban stem cell research that would help her son.

“Scott Walker’s extreme opposition to embryonic stem cell research is out of step with the scientific community and Wisconsin’s mainstream,” Barrett said Tuesday in a statement.

Walker has called Barrett’s ad an “outright lie” because he supports research that doesn’t involve destroying an embryo. He said Tuesday that adult stem cell research holds more promise for diabetics like his wife as well as people suffering from other diseases.

“Science has clearly shown us the greatest path toward a cure for my wife and others is adult stem cell research,” Walker said. “That’s where the greatest scientific exploration has been. We can do that, we can be a leader in Wisconsin and still do it ethically.”

On Tuesday, the governor asked a federal judge for permission to file a friend-of-the-court brief in the fight over the future of embryonic stem cell research, arguing that stopping it would cost the state millions.

U.S. District Judge Royce Lamberth in Washington, D.C. entered an injunction in August blocking federal funding for embryonic stem cell research. That order was put on hold by a federal appeals court while it considers an appeal from President Barack Obama’s administration.

Sande, the Pro-Life Wisconsin official, said he wasn’t worried about how Walker couched his position on the issue.

“I think candidate Walker is just trying to focus on the positive aspects of stem cell research,” Sande said.