Sanders called Trump's policies "pathetic" on Monday, and argued that he would enrich billionaires while ignoring the working class, according to a Washington Post report.
Trump and Sanders have been at it since Sunday, when Sanders said that Trump's followers were misguided and that his policies would benefit them more. He pointed that Trump is against the minimum wage and supports cutting taxes for the rich, something that wouldn't benefit lower and middle class supports of Trump. He made the comments on "Face the Nation."
Trump fired back at Sanders, calling him a "wacko" on his Twitter account. He mocked Sanders, claiming that his allies are "coming over to me" because he's lowering taxes while Sanders will raise them.
He again called Sanders a wacko at a rally in New Hampshire, and warned of "massive tax increases" if Sanders is elected.
Sanders responded to Trump's comments by calling him a "pathological liar" who is "nervous" that America is catching on to him. He again slammed him for giving billionaires tax breaks while refusing to raise the minimum wage.
Sanders also took aim at Trump for his controversial comments on race and religion, telling attendees of his rally that "we're not going to hate Latinos, we're not going to hate Muslims, we are going to stand together."
Income inequality has been a key platform in Sanders campaign, who is still seen as an upset bid over Hillary Clinton despite a strong following. Sanders describes himself as a democratic socialist.