The former Secretary of State and the New York congresswoman are supporting rival candidates for the Democratic nomination in the race to fill Housing and Urban Development Secretary Marcia Fudge’s old seat.
Ms Clinton has thrown her weight behind Cuyahoga County Council member Shontel Brown to represent Ohio’s 11th Congressional District.
“I’m proud to endorse (Brown) for Congress in the OH special election,” Ms Clinton tweeted. “Shontel made history as the first Black woman to chair her county Dem party, and she’ll work to help her state and our country recover from COVID.”
Ms Brown welcomed the endorsement from Ms Clinton, who she volunteered for during her presidential campaign in 2016.
“Secretary Clinton has been a champion for working families for her entire career, and I am incredibly honored to receive her endorsement,” said Ms Brown after the endorsement.
“As a volunteer for her campaign in 2016, I was inspired by her message to put women at the head of the table, finally.”
Ms Ocasio-Cortez, however, has thrown her support behind former Democratic state Senator Nina Turner, who has also been endorsed by Senator Bernie Sanders.
Earlier this year the New York lawmaker described Ms Turner as a “bold, unapologetic progressive who has spent her entire career advocating for the working people of Northeast Ohio.”
She also described her as “a powerful voice for progressive values and policies that will make a meaningful difference in the lives of working people across the country – like Medicare-for-All, a $15 minimum wage, and a Green New Deal.”
The primary election is taking place on 3 August, and the general election will be contested on 2 November.