Former Vice President Joe Biden appeared to stumble over his words while discussing the economy and taxes on Tuesday night. "Why should someone who's clipping coupons in the stock market may, in fact, pay a lower tax rate than someone who in fact is, like I said, a schoolteacher and a fireman? It's ridiculous," Biden said. Biden made those comments while appearing at the fourth Democratic debate. Biden has long been the frontrunner for the Democratic nomination but is facing a potential challenge Sen. Elizabeth Warren, D-Mass., who has been gaining traction in key states.