Not only refused to denounce them, he claims to have know knoledge about them, using the "just play dumb" strategy.
OOps, Trump in 2000:
Mr. Trump painted a fairly dark picture of the Reform Party in his statement, noting the role of Mr. Buchanan, along with the roles of David Duke, a former leader of the Ku Klux Klan, and Lenora Fulani, the former standard-bearer of the New Alliance Party and an advocate of Marxist-Leninist politics. “The Reform Party now includes a Klansman, Mr. Duke, a neo-Nazi, Mr. Buchanan, and a communist, Ms. Fulani,” he said in his statement. “This is not company I wish to keep.”
That would have been a good statement for today instead of playing dumb.