Ryan Lovelace has a very interesting piece up gaming out possible GOP responses to a possible Obama executive action. At this stage of the game, much of the debate focuses on the use of a continuing resolution on the budget that would include a prohibition on using government funds to support portions of an executive order (such as the printing of work-authorization cards).
Of course, opponents of a presidential power grab are not just playing the inside-the-Beltway game. They are also working to mobilize public opinion, as this column by Alabama's Jeff Sessions suggests.