Cindy McCain, the wife of Arizona Senator John McCain, is slated to appear in the Phoenix reading of a play based on the trial over the constitutionality of California's gay marriage ban, Proposition 8.

8, which was written by Academy-award winning screenwriter Dustin Lance Black (Milk), uses actual court transcripts from Hollingsworth v. Perry and first-hand interviews to document the 2010 trial which struck down the constitutional amendment approved by voters two years earlier.

After a number of appeals, the Supreme Court last month heard oral arguments in the case and is expected to hand down a ruling in June.

Senator McCain, a Republican, is opposed to marriage equality. His wife and their daughter, Meghan McCain, on the other hand, have expressed their support.

(Related: Meghan McCain threatens to leave GOP over social issues, including gay rights.)

The Phoenix reading of 8 is being produced by Neil Giuliano, the former president of GLAAD, and proceeds from sales benefit the American Foundation for Equal Rights (AFER), the group formed specifically to challenge Proposition 8.