NEW YORK CITY - SEPTEMBER 3 2015: Republican candidate for president Donald Trump announced he had signed a pledge not to run as an independent candidate should he fail to win the party's nomination in 2016.

Democratic vice-presidential nominee Tim Kaine had a simple question for business mogul Donald Trump on Wednesday night.

“Does anybody in this massive auditorium believe that Donald Trump’s been paying his fair share of taxes?” Kaine, a senator from Virginia, said at the Democratic National Convention, as the crowd screamed “No.” “Do you believe he ought to release those tax returns like every other presidential candidate? Of course he should. Donald Trump, what are you hiding?”

Trump, the Republican nominee, reiterated during a Wednesday news conference he would not release his tax returns, citing an ongoing audit from the Internal Revenue Service.

CNBC