South End state Rep. Jon Santiago is throwing his vote to Acting Mayor Kim Janey after ending his mayoral campaign in July.

The State House lawmaker, who is also a Boston Medical Center physician, plans to formally endorse Janey in Boston’s Villa Victoria housing development on Wednesday. Janey became acting mayor in March after Marty Walsh left for the labor secretary job in President Biden’s cabinet.

“She is leading Boston through the pandemic — helping ensure that 70% of residents have gotten at least one shot while implementing bold measures to take on the Delta variant,” Santiago said. “She is delivering results to combat the housing crisis and doing so with empathy and resolve. And she is committed to a Boston that is both equitable and just.”

The endorsement comes hours before the five major remaining candidates for mayor take the stage at NBC10’s studios for a televised debate. The Dorchester Reporter and the Bay State Banner are partnering with NBC10, New England Cable News (NECN) and Telemundo. The hour-long debate will be broadcast live at 7 p.m. on NBC10 and NECN.

Janey said in her own statement that she is “grateful to have his thoughtful counsel and valuable support” as the campaign heads into its final week.

“From the emergency room of Boston Medical Center, to the halls of the State House, to the streets of his own neighborhood, Jon has always stood on the front lines in the fight for a better Boston,” she said. “I am grateful to have his thoughtful counsel and valuable support as we work together to address the [intersecting] crises of substance use and homelessness, build housing every family can afford and have schools where every child can thrive.”

Because he dropped out after the deadline for withdrawing names from the ballot, Santiago’s name will still appear with the other mayoral candidates on Sept. 14. The preliminary will narrow the field to two finalists who will face off on Nov. 2.

The other candidates are City Councillors Andrea Campbell, Annissa Essaibi George and Michelle Wu, and former city economic development official John Barros.