When I meet William Johnson in his downtown Los Angeles law offices, he’s unfailingly polite.

But the picture changes when you ask Johnson about his views on politics and race.

“Yes, I am a white nationalist,” Johnson says. “I support the interests of the White Western European peoples.”

Johnson is one of the best-known white supremacists in the US and the chairman of a political organization called the American Freedom Party. Its roots go back to Southern California’s Nazi skinhead movement of the 1980s — and it advocates for the separation of the races and an end to all immigration, both illegal and legal.

“We have in Europe, and every traditionally white country, a dramatic shift in that the founding population is being replaced by immigrants, refugees, other peoples, so, really, the white race is in peril worldwide. I want a separate white ethno-state, but I want to keep Western civilization alive.”

Although the American Freedom Party is fielding its own candidate for the presidency, most of its members, including Johnson, are supporting the campaign of Donald Trump.

“Donald Trump is the closest candidate to our position that is mainstream,” Johnson says.

When I ask Johnson what he likes about Trump's positions, he responds that "it is primarily the race issue."

"He is saying we need to build a wall. We need stop Muslims from coming in. He is saying things that are good from the perspective of trying to maintain the integrity of the founding stock of this nation."

While the American Freedom Party is operating without the support or blessing of the Trump campaign, Johnson and his allies have organized in a very politically conventional way.

"We’ve set up a separate white nationalist super PAC called the American National Super PAC," Johnon says.

The super PAC is bankrolling robocalls to voters in states holding primaries and caucuses.

This is part of one message that greets voters:

The American National Super Pac makes this call to support Donald Trump….The white race is dying out and America because we are afraid to be called racist….Donald Trump is not a racist, but Donald Trump is not afraid. Don’t vote for a Cuban. Vote for Donald Trump.

Experts who study hate groups in the US say the American Freedom Party’s support for Trump is just one example of a wide and enthusiastic embrace of the controversial candidate by white nationalists.

"There are people on the far racist right who describe Donald Trump as our 'glorious leader.' They actually seem to think he is Hitler without the mustache and slightly dressed up in American clothing," says Mark Potok, a senior fellow at the Southern Poverty Law Center, which monitors hate and white nationalist groups in the US, including the American Freedom Party.

Potok says although the American Freedom Party is virtually invisible to the political mainstream, it is well known on the ideological fringe and rejects the usual trappings of traditional racist groups, giving weight to its support for Trump.

"The American Freedom Party is arguably the most important white nationalist party in the United States," Potok says. "By white nationalists, I mean groups that don’t dress up in Nazi uniforms, don’t dress up in Klan hoods, wear the veneer of intellectual sophistication. Don’t use ugly epithets. That said, the American Freedom Party is plainly as extreme, or more extreme, than the Klan."

Johnson says support for Donald Trump will likely grow among white nationalists as the campaign continues. But he says Trump is doing so well during the primary season, he doesn’t expect that his white nationalist political action committee will really need to spend much more to support him.

“Donald Trump is such a formidable candidate now that it might be superfluous to continue doing robocalls for his campaign.”

But Johnson adds that his support won't stop there.

"We’ll be supporting him … We will still be supporting him as we can."