Texas Southern University has canceled a commencement speech by Senator John Cornyn, a high-ranking Republican in the U.S. Senate, which was planned for Saturday.

According to a student petition, which has garnered 859 signatures, "The decision to host Mr. Cornyn as a keynote speaker sends the message that the policies and views he has advocated and supported, including both discriminatory policies and politicians, are acceptable by the university and subsequently the student body." That petition, coupled with the concern over a potential confrontation, led university officials to cancel Sen. Cornyn's keynote address.

"Every consideration is made to ensure that our students’ graduation day is a celebratory occasion and one they will remember positively for years to come," the university wrote in a statement posted to Facebook. "We asked Senator Cornyn to instead visit with our students again at a future date in order to keep the focus on graduates and their families."

Texas Southern University is one of the largest historically black universities in the country and confers the fourth-largest number of doctoral and professional degrees to African Americans. 

Rebecca Treviño, who is graduating with a degree in social work, said she and a group of others from her social work classes decided to start the petition to raise awareness about Cornyn's stance on key issues. "I don’t know if people were aware that he supports a lot of discriminatory policies and practices," Treviño says. "He has a lot of power and people need to see that what he stands for doesn’t align with or reflect the values of TSU students."

The petition listed several reasons why Cornyn would be a poor choice for commencement speaker, including his disapproval of former Supreme Court Justice Thurgood Marshall, for whom Texas Southern's law school is named. "This is our graduation," the petition reads. "We have the right to decide if we want to refuse to sit and listen to the words of a politician who chooses to use his political power in ways that continually harm marginalized and oppressed people." 

U.S. Representatives Al Green and Sheila Jackson Lee are still slated to speak.