Fresh from a controversy over his views on evolution, Wisconsin Republican Gov. Scott Walker is now involved in a controversy over his views, or lack of them, on President Obama's religion. On Saturday, two Washington Post reporters asked Walker, in the nation's capital for a governor's meeting, whether Obama is a Christian. Walker said he didn't know.

Informed by the reporters that Obama is in fact a Christian, Walker replied, "I've actually never talked about it or I haven't read about that," protesting that the president's religion is not a topic of great interest to voters. "I would defy you to come to Wisconsin. You could ask 100 people, and not one of them would say that this is a significant issue," Walker told the Post.

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Nevertheless, the story created at least a minor explosion in the political press, and Democrats quickly used it to attack a Republican who has recently risen to the top tier of the GOP 2016 presidential field.

But when it comes to confusion, or wrong information, about Obama's religion, Scott Walker is far from alone. Polls have long shown many Americans know little about the president's faith.

In June, 2012, Gallup asked, "Do you happen to know the religious faith of Barack Obama?" Forty-four percent said they did not know, while 36 percent said he is a Christian, 11 percent said he is a Muslim, and eight percent said he has no religion. The "don't know" group included 36 percent of Democrats. (A larger number of Republicans, 47 percent, said they didn't know Obama's religion, as did 46 percent of independents.)

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In August, 2010, a Pew poll made news when it found that 18 percent of those surveyed believed Obama is a Muslim. But just as notably, 43 percent of respondents in that survey told Pew they didn't know Obama's religion. Among those who said they didn't know were 41 percent of Democrats.

One notable suggestion in the Pew survey was that in Obama's first couple of years in office, as Americans became more familiar with him as president, they became less sure of his religious faith. In March 2009, shortly after Obama entered the White House, 34 percent said they did not know his religion, while 48 percent identified him as a Christian. By August 2010, the number of Americans who said they did not know Obama's religion had grown to 43 percent, while the number who identified him as Christian fell to 34 percent. The trend was true not just of the president's political opponents but of his supporters as well. "Even among Democrats, fewer than half (46 percent) now identify his religion as Christian, down from 55 percent last year," Pew wrote in 2010.

In June 2012, Pew asked the question again and found that 36 percent — still more than one-third of Americans — did not know Obama's faith, while 45 percent identified him as a Christian. (The poll, taken during the 2012 presidential campaign, found that more people — 51 percent — correctly identified Mitt Romney as a Mormon than the 45 percent who said Obama is a Christian.)

The polls are anywhere from two to four years old. There hasn't been much research on the topic recently, so it's possible views have changed in one direction or the other.

Whenever the issue pops up, Obama's most ardent supporters are quick to blame conservative media for misperceptions about Obama's religion. But it's possible something in Obama's public presentation of himself has also created confusion among a significant number of Americans about his religion. The fact is, Obama's religious roots and development have always been a complicated story. In 2010, after the Pew poll came out, I wrote about the causes of public confusion about Obama and faith, particularly the belief that he is a Muslim:

In 1985, Barack Obama had just arrived in Chicago for his new job as a community organizer when he headed to Smitty's Barbershop, a tiny storefront on the South Side. As Smitty cut his hair, Obama listened to the men in the shop talk politics and racial grievance. When the barber finished, he handed Obama a mirror and said, "Haircuts ten dollars. What's your name, anyway?"

"Barack."

"Barack, huh," Smitty responded. "You a Muslim?"

"Grandfather was," Obama said, according to his memoir Dreams From My Father.

Smitty's question, which Obama didn't exactly answer, prefigured a controversy that continues to this day.

A new poll by the Pew Forum on Religion and Public Life shows that 18 percent of Americans believe Obama is a Muslim. That is up from the 12 percent who believed that in October 2008, just before Obama was elected president.

At the same time, the number of Pew respondents who say Obama is a Christian — in Dreams From My Father, he describes his conversion to Christianity under the tutelage of the Rev. Jeremiah Wright — has declined from 51 percent in October 2008 to 34 percent now. And the number of people who say they don't know Obama's religion is growing, from 32 percent back then to 43 percent today.

The White House blames the situation on a "misinformation campaign" from Obama's opponents. But Obama and his aides might also blame themselves for the way they've handled the Muslim issue over the years.

The question did not come out of nowhere. As Obama said, his grandfather was a Muslim. His father was raised a Muslim before becoming, by Obama's account, "a confirmed atheist." Obama's stepfather was a Muslim. His half-sister Maya told the New York Times that her "whole family was Muslim."

Obama spent two years in a Muslim school in Indonesia and later, in a conversation with the Times' Nicholas Kristof, described the Arabic call to prayer, the beginning of which he recited by heart, as "one of the prettiest sounds on Earth at sunset." Given all that, it is entirely accurate and fair to describe Obama as having Muslim roots.

Yet during the [2008] campaign his aides shouted down even a measured discussion of the topic, and Obama's critics could face ostracism simply for uttering the candidate's middle name. In December 2007, with the Iowa caucuses approaching, former Democratic Sen. Bob Kerrey, a Hillary Clinton supporter, said of Obama, "I like the fact that his name is Barack Hussein Obama, and that his father was a Muslim and that his paternal grandmother is a Muslim. There's a billion people on the planet that are Muslims, and I think that experience is a big deal." Kerrey's remarks caused an uproar — one TV commentator wondered whether they were "poisoning the well" — and Kerrey later apologized.

Eighteen months later, when President Obama traveled to Cairo for a long-awaited speech to the Muslim world, the White House was saying, and the press was reporting, the same thing Kerrey had to apologize for. "President Obama is now embracing his Muslim roots," ABC News "Nightline" announced. "President Obama's speech was laced with references to the Quran and his Muslim roots," said USA Today. "Obama touched on his own Muslim roots," reported the Associated Press.

Many people do not pay close attention to news reports. It's entirely possible some of them blurred the distinction between "Muslim roots" and "Muslim," especially since Obama in Cairo celebrated what his campaign had once downplayed.

In the more than four years since that column was published, it's likely at least some confusion about Obama's religion has persisted. For one thing, few people see Obama openly practicing any religious faith. After the president did not attend church on Christmas 2013, the New York Times, citing unofficial White House historian Mark Knoller, noted that Obama had attended church 18 times in nearly five years in the White House, while George W. Bush attended 120 times in eight years. Yes, there are a variety of reasons some presidents don't go to church very often, but in Obama's case, absence does nothing to change existing public perceptions of him.

And there are other factors. For example, it would not be a stretch to guess that those Americans who told Gallup and Pew that they did not know the president's faith would remain unsure after hearing reports that at the recent National Prayer Breakfast, Obama explained Islamic State violence by urging listeners to "remember that during the Crusades and the Inquisition, people committed terrible deeds in the name of Christ." Again, many people don't pay close attention to the news, and snippets of reports on Obama's faith, like his remarks at the Prayer Breakfast, could yield a confused picture.

Some would argue that, while yes, many in the public don't know the president's religion, certainly Scott Walker, the governor of a state, should know. But Walker's answer to the reporters' question just reflects a broader public puzzlement over Barack Obama's faith — a phenomenon that he helped perpetuate and, at this late date in his presidency, seems unlikely to go away.

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