I think Rubio’s accusation is general, referring to the campaign. I’m sure he wants people to also view the Trump U case, but I don’t think his “con man” accusation is limited to that.
I think Rubio is trying to be like Trump with trying to put a label on Trump like Trump did with Cruz (liar) and Jeb (low-energy). Rubio and Cruz are trying to throw things at the wall like spaghetti to see what will stick and in hopes of getting free media attention. Trump can pull it off because it was true, Rubio can’t. I’m not an attorney but I think that Trump could threaten a lawsuit but it wouldn’t stick because there are different rules for defamation and/or libel (sorry, don’t remember) for famous or political people than there are for us peons.