Donald Trump blamed a faulty television earpiece on Monday for his failure to disavow support from a white supremacist, swatting aside the latest controversy to shadow his unorthodox march toward the Republican presidential nomination.

On the eve of the biggest voting day in the race to pick the 2016 U.S. presidential candidates, the Republican front-runner tried to explain why he did not condemn backing from former Ku Klux Klan leader David Duke during a Sunday television interview.

"I'm sitting in a house in Florida with a very bad earpiece that they gave me, and you could hardly hear what he was saying, but what I heard was various groups," Trump said on NBC's "Today" show.