The document discusses the history and politics surrounding the mortgage interest deduction (MID) in the US tax code. It begins by explaining that the MID was originally an unintended consequence of the 1913 Revenue Act, which allowed the deduction of all interest paid, including mortgage interest. Over time, as homeownership increased, the MID became codified in American culture and politically difficult to reform despite its inefficiencies. The document aims to analyze the political history and alternatives to the MID.