MIT economist Jonathan Gruber Call it an Obamacare showdown.Two leading voices in the controversy over President Obama's signature healthcare law will face off next week at an event likely to grab widespread attention. One of them contributed to crafting the law. The other is trying to get a major part of it struck down.Jonathan Gruber, an economics professor at the Massachusetts Institute of Technology, will appear side-by-side with Michael Cannon, director of health policy studies at the libertarian Cato Institute.