The individual mandate started as a Republican idea to fix health care, but it was at the heart of a Democratic president’s signature measure. Now Congress is using the tax bill to kill the mandate. Why did Republicans turn on their own big idea, and what does it mean for the future of the Affordable Care Act?

Guests: Margot Sanger-Katz, a health care reporter for The Times; Jonathan Gruber, a professor of economics at M.I.T. who advised Mitt Romney’s team on overhauling health care in Massachusetts, and the Obama administration in drafting the Affordable Care Act. For more information on today’s episode, visit nytimes.com/thedaily.