White House press secretary Karoline Leavitt slammed JFK’s grandson Jack Schlossberg for his “ridiculous comments” about the Trump administration after he launched his Manhattan congressional bid Wednesday. Schlossberg, 32, is the only grandson of President Kennedy, whose nephew Robert F. Kennedy Jr. serves as Trump’s secretary of health and human services. Schlossberg trashed his elder relative as a “rabid dog” and called the Trump administration “the most corrupt in American history” as he rolled out his campaign. “I don’t even think such ridiculous comments are worth responding to. Obviously those things are not true,” Leavitt told The Post at her regular briefing.