San Francisco Supervisor Connie Chan and state Sen. Scott Wiener are set to debate Thursday night as they compete for the congressional seat held by Speaker Emerita Nancy Pelosi for nearly four decades.

The two Democrats will meet just days before mail ballots begin arriving for the November election. The contest is described as the first genuinely competitive race for the seat in years.

The debate is scheduled to begin at 7:30 p.m. and will be streamed live on YouTube. Planned topics include affordability, technology and the economy, immigration, conflicts abroad, and San Francisco’s role in national politics.