CAMBRIDGE, Mass. — Top strategists from the campaigns of Donald J. Trump and Hillary Clinton, interrupting each other and sometimes raising their voices, engaged in an angry debate on Thursday about how Mr. Trump pulled off his upset victory.

Emotions were still raw at the campaign post-mortem, held at Harvard’s Institute of Politics, particularly over the influence of Stephen K. Bannon, who left Breitbart News — which he has called a “platform” for the white nationalist alt-right — to help run Mr. Trump’s campaign.

Mr. Bannon will serve as a senior aide to Mr. Trump. David Bossie, Mr. Trump’s deputy campaign manager, called Mr. Bannon a “brilliant strategist.”

That provoked the Clinton campaign’s director of communications, Jennifer Palmieri, to respond, “If providing a platform for white supremacists makes me a brilliant tactician, I am more proud to have lost.”