One set of lawsuits accuses the Internal Revenue Service of illegally implementing new subsidies to help people buy insurance. Separately, more than 60 lawsuits have been filed challenging the law’s mandate for health plans to cover birth control.

A loss for the administration on the contraception mandate would undermine a key selling point for the law that Democrats used to court women in the 2012 elections.

The challenge to the law’s insurance subsidies, while more obscure, poses a far bigger and more dangerous threat to the Affordable Care Act.

Simon Lazarus, senior counsel at the Constitutional Accountability Center, has argued that there’s a very real chance the Supreme Court’s conservative majority would strike down the IRS’s approach to insurance subsidies if it gets the chance.