Wisconsin Gov. Scott Walker flashes a double thumbs-up during the Freedom Summit in Greenville, S.C., on May 9. (AP Photo/Rainier Ehrhardt)

Scott Walker has been criticized for dramatically changing his stance on immigration: First, he supported granting citizenship to the millions of undocumented workers already in the country. Then he was opposed to it and acknowledged that his position had changed. Then there were reports that he had privately expressed support once again. Now he wants all undocumented workers to return to their home countries and legally apply to enter the U.S. -- and has suggested further limits on legal immigration.

So that's why during a Tuesday evening interview on Fox News, host Bret Baier asked Walker: “If you’re willing to flip-flop… on such an important issue like this, how can voters be sure that you’re not going to change your position on some other big issues?”

Walker responded: “Well, actually, there’s not a flip out there."

Walker then explained that his early comments on immigration came years ago when he gave "a quick momentary reaction" as a county official and then again as a new governor of Wisconsin, two positions that he says don't require deeply researched immigration position. Now that he's thinking about running for president, Walker said he has learned much more about the issue by talking with border-state governors, members of Congress and other experts.

“A flip would be someone who voted on something and did something different," Walker said. "These are not votes... I don’t have any impact on immigration as a governor. I don't have any impact as a former county official. I would be if I were to run and ultimately be elected as president."

Immigration isn’t the only issue where Walker has shifted his stance. During his first years as governor of Wisconsin, Walker did not publicly raise any concerns about the Common Core education standards being implemented in the state -- and, at times, he appeared to embrace the reforms. But then during his reelection campaign last year, Walker called for a full repeal of Common Core. Now he’s pushing to allow school districts to only use the standards if they choose to do so.

And on the campaign trail, Walker has been answering questions about his abortion stances and a 2014 campaign ad that featured him looking directly into the camera and saying: "Hi, I'm Scott Walker. I'm pro-life. But there's no doubt in my mind the decision of whether or not to end a pregnancy is an agonizing one. That's why I support legislation to increase safety and to provide more information for a woman considering her options. The bill leaves the final decision to a woman and her doctor."

Two days after being asked about this ad in television interview, Walker released an open letter reiterating his anti-abortion stances and called for a ban on all abortions after 20 weeks -- an issue he had dodged on the campaign trail.