The Rev. Al Sharpton, GOP strategist Margaret Hoover and Baltimore Ravens linebacker Brendon Ayanbadejo are among those expected to speak outside the U.S. Supreme Court on Tuesday as it considers the first of two cases related to gay marriage.

The court will hear oral arguments Tuesday in a case challenging the constitutionality of Proposition 8, a constitutional amendment approved by California voters in 2008 which defines marriage as a heterosexual union. The following day, Wednesday, the court will consider a challenge to the Defense of Marriage Act (DOMA), which prevents the federal government from recognizing the legal marriages of gay and lesbian couples.

The United for Marriage rally will kick off at 8:30AM outside the Supreme Court.

Ayanbadejo told gay weekly the Washington Blade that he is “excited” to speak at the rally.

“I've gone out to the polls and passed out fliers and done stuff like that, but I've never spoken in front of a courthouse or in any type of rally ever before,” Ayanbadejo said Monday. “This is sort of uncharted territory for me.”

(Related: Brendon Ayanbadejo: We're “laying the foundation” for an openly gay NFL player.)

Also expected to speak are Republican strategist David Frum, Outserve-SLDN Executive Director Allyson Robinson, Bishop V. Gene Robinson and Washington National Cathedral dean Gary Hall.