Hey, why not? In addition to being a bomb-throwing liberal, Alan Grayson's pedigree is as a trial lawyer. Suing because he's mad about something seems pretty natural for a guy like that. And since Democrats have treated the last three congressional elections as largely illegitimate - favoring executive actions by Obama to get around the "obstructionist" yet duly elected majorities - why not seek a way to throw out the election of a Republican president?
Especially delicious, of course, is that this is all based on the birther nonsense that they find appalling when it's aimed at Obama, but can't embrace quickly enough when Ted Cruz is the issue: