Duke, a former neo-Nazi who unsuccessfully ran for the U.S. presidency in 1988 and 1992, served a year in prison in 2003 and 2004 after pleading guilty to tax fraud and stealing hundreds of thousands of dollars in donations from supporters to pay gambling debts. (from The Huffington Post 
The Southern Poverty Law Center also thinks Duke is a Neo-Nazi.
David Duke is the most recognizable figure of the American radical right, a neo-Nazi, longtime Klan leader and now international spokesman for Holocaust denial 
David Duke is a former Grand Wizard of the Terrorist KKK. . He twice ran for President, has run for Governor, Senator, and has sat on the Louisiana state legislator. He has run as both a Republican and a Democrat. He is very, very hard-core conservative.
David Duke is a weak character who had trouble paying his gambling debts. That's right folks, his supporters gave Duke money hoping he'd use the money to spread racist poison, then Duke used some of that money to pay off gambling debts instead. Ma Ha Ha! 
In 1980 Duke formed the White supremacist National Association for the Advancement of White People, and all that has resulted is the human race has been embarrassed. What has followed is 27 years of more racist junk that doesn't benefit anyone's intelligence.
Duke and Stormfront
David Duke also helped fellow white supremacist Don Black create the notorious white supremacist website Stormfront, aimed at advancing, biased, and nonsensical beliefs ranging from falsely claiming that the Ancient Egyptians were really Anglo-Saxons, not Africans, to attempting hopelessly to explain the fact that East Asians are on average more intelligent and less crime-prone than whites by claiming that all Asians are really of caucasian ethnicity, somehow.
Stormfront and Obama
When it comes to Duke and Stormfront, some of the biggest hilarity comes from the website's frustration when Obama, an African-American, was elected and inaugurated President of the United States of America. Stormfront promptly locked itself and its members into their own happy little world by pretending that Duke, their hero, became president.
The following headline was posted on the website's front page almost immediately after the January 20th inauguration:
"President David Duke Gives Alternative Inaugural Address!"
All of us genuinely intelligent, anti-racist individuals have three words for all you Stormfronters and Duke worshipers out there in response to this sad display:
GET OVER IT.
Duke Imagines that Zionist Jews are the cause of things like New World Order 9/11 7/7 & other stuff that sensible people know is nothing to do with Jews. However RationalWiki debunks these bogus claims. See International Jewish conspiracy.
Despite the Racism and other garbage Duke is mixed up with he insists he's a Christian.  RationalWiki and Wikipedia both say he's a Christian.   Some people do bad things in the name of Christianity.
He also has a very small peen. Well, er.. we aren't sure about that and we aren't attracted to Duke so we aren't likely to find out.