Via Politico:

For President Barack Obama’s ground-breaking interview on gay marriage, the White House turned to a friendly face - ABC’s Robin Roberts. ...

By giving the interview to an African-American and Christian - two groups whose opposition to same-sex marriage has been significant - the White House may have been aiming to make Obama’s announcement more palatable to groups that differ with his support for gay marriage. (Christianity has long played a central role in Roberts’ life — she has credited her success to her parents’ emphasis on the three “D’s”: Discipline, Determination, and “De Lord.”)

It was on Tuesday that the White House called ABC News to see about setting up an interview with Roberts, according to Talking Points Memo.