Wisconsin Gov. Scott Walker is the leader in some national polls for the 2016 Republican presidential nomination. He's also the least-known candidate in some surveys. There could be a relationship between those two factors.

Start with the new Fox News poll, done the last few days of March. Pollsters gave respondents, all registered voters, a list of seven Republican candidates — Rand Paul, Mike Huckabee, Jeb Bush, Marco Rubio, Ted Cruz, Walker and Ben Carson. "Please tell me whether you have a generally favorable or unfavorable opinion of each one," the pollsters asked. And then they added, "If you've never heard of one, please just say so."

Forty-three percent of respondents said they have never heard of Walker — the highest of any GOP candidate except Carson, with 54 percent. In addition, ten percent said they "can't say" their opinion of Walker. (Bush's never-heard-of number was eight percent, with ten percent "can't say.") Walker's total was 27 percent favorable, 21 percent unfavorable, with a combined 53 percent never-heard-of or can't-say.

Then look at the ABC News-Washington Post poll done a few days before the Fox survey. In that, pollsters asked adults the favorable-unfavorable question about six Republican candidates — Bush, Rubio, Walker, Cruz, Paul and Chris Christie — and added the category of "no opinion." Walker had by far the highest number of people who said they have no opinion of him — 47 percent to Bush's 14 percent. (By the way, Walker's rating was 24 percent favorable versus 38 percent unfavorable.)

Finally, there is a CNN poll taken a few days earlier, which asked adults about seven candidates — Bush, Walker, Carson, Christie, Huckabee, Paul and Rubio. After Carson, Walker had the highest "never heard of" rating, with 48 percent. (An additional 10 percent said they had no opinion of him.) Walker's total number was 21 percent favorable, 21 percent unfavorable, and 58 percent never-heard-of or no-opinion.

For a candidate who starts out with little national recognition, a campaign is a long process of telling voters who he is. With the general public — and all three polls cited above were of the public, not just Republicans — Walker is still a mystery for a large number of people. Even some Republicans who know of Walker and like him base their opinion on what they know about Walker's stand against public-sector unions in Wisconsin, and little beyond that. Despite all the attention the media has paid to the campaign so far, Walker is still starting out when it comes to explaining to voters who he is and why he's running.