Supreme Court Justice Sonia Sotomayor recused herself from an upcoming case that will affect the Electoral College, citing a potential conflict of interest.

The Colorado court case, which will be heard next month, will rule whether the U.S. Constitution forbids states from dictating how members of the Electoral College cast votes for president. The question before the court is if electors, or those who ultimately cast the Electoral College votes, are mandated to cast those votes for the candidate who won the popular vote.

[Related: Ted Cruz says popular vote compact 'probably' unconstitutional]

Sotomayor recused herself as a result of a long-time friendship with one of the parties in one of the cases. The acquaintance, Polly Baca, was one of three electors who argue that they should be able to vote for the candidate of their choice rather than the candidate who won the popular vote in the state. Baca and Sotomayor have been friends for decades, with Baca's sister and her family living in Sotomayor's New York apartment, according to NBC News.

“The justice believes that her impartiality might reasonably be questioned due to her friendship with respondent Polly Baca,” Supreme Court Clerk Scott Harris wrote. “The initial conflict check conducted in Justice Sotomayor’s Chambers did not identify this potential conflict.”

The 10th U.S. Circuit Court of Appeals invalidated Colorado's law requiring conformance with the popular vote, but, faced with a similar challenge, Washington state's Supreme Court upheld that state's similar law.

There is an additional case that the Supreme Court will take up on this issue, and Sotomayor will participate in that decision.