Arizona Libertarian Party v. Reagan

The AZLP (coplaintiff) told election officials in August 2012 that it planned to challenge a new signature-requirement law's constitutionality, but didn't actually file suit until April 2016, then sought an emergency injunction less than three weeks before the nomination deadline; Reagan (defendant) raised laches, arguing the delay prejudiced her ability to develop a defense and left the court too little time to properly resolve the constitutional question before the deadline.