Republicans have embraced a new test for tax reform, one that could add to the already immense difficulty of passing legislation: They will say their reform bill must make the tax code even more progressive than it is today.

A senior administration official told reporters Tuesday that the goal of the joint framework developed by the Trump White House and Republican congressional leadership is meant to be “a middle-class tax cut that is at least as progressive as the current system and that doesn’t shift the tax burden from higher-income to lower-income households.”