David Duke on Monday reiterated his support for the presidential campaign of real estate developer Donald Trump .

The former Louisiana state representative and one-time Ku Klux Klan leader told listeners on his radio show that "it's very, very important that [Trump] wins this election, both for the Republican nomination, and it's important for him to win the presidency of the United States.

Voting for Trump, Duke said, "is the best thing we can do to prevent the spread of mass immigration and the conspiracy of "international bankers, a term white supremacists use to refer to Jewish people. Right Wing Watch first reported on the comments .

Trump has come under fire in recent days for his reluctance to condemn Duke and the white supremacist movement during a Sunday talk show appearance. Asked whether he would disavow his support from Duke and the Ku Klux Klan, Trump played dumb, telling CNN , "You wouldn't want me to condemn a group that I know nothing about. ... I will do research on them and certainly I would disavow if I thought there was something wrong."

On Monday, Duke put the 2016 presidential race in the context of "a struggle for the survival of European mankind," or white people. Duke also said that Trump's nativist candidacy has made it easier for racist people to express racist views in public, without worrying about public disapproval.

Trump's candidacy, Duke said, is "encouraging people to begin to speak frankly and honestly about some of the issues we must talk about if we're going to survive as a nation and as a people."

While Duke is among Trump's most vocal supporters in the white nationalist movement, experts say it's hard to get a good sense of how many other white supremacists are supporting Trump because of the social stigma around racism.

"The things Trump says that are white nationalist in tone have found their desired audiences," said Mark Potok, a senior fellow at the Southern Poverty Law Center, a nonprofit that monitors extremists and hate groups.

"But don't expect to see many more of these white supremacists to step into the public eye," he said. "As soon as they are exposed, they become pariahs, so it's better for them if they stay in the background."

Trump is poised to win a significant number of Republican delegates Tuesday in more than a dozen nominating contests across the country.

His upstart presidential campaign first gained national attention last year, after he exploited anti-immigrant sentiment in the U.S. Since then, Trump's proposal to ban Muslims from entering the country and his promise to build a wall between the United States and Mexico have both helped make him an appealing candidate to white nationalists.

CORRECTION: A previous version of this article incorrectly stated that Duke was a former congressman. He is a former state representative.

Editor's note: Donald Trump is a serial liar , rampant xenophobe , racist , misogynist, birther and bully who has repeatedly pledged to ban all Muslims -- 1.6 billion members of an entire religion -- from entering the U.S.