Pennsylvania's brief history of hosting presidential debates

Flashback: Philadelphia last hosted a presidential debate in 1976 between Democrat Jimmy Carter and Republican President Gerald Ford at the Walnut Street Theatre.

• Their debate was marred by a technical glitch that led to 27 minutes of silence.
• Barack Obama also debated Hillary Clinton here during the 2008 Democratic primary, before securing the party's nomination.

Zoom out: Missouri and New York have hosted the most presidential debates since the first was televised in 1960.

Between the lines: The Commission on Presidential Debates has organized general election debates since 1988.

• The nonpartisan group has preferred to hold three presidential debates and a vice presidential debate, mostly on university campuses, every cycle, political analyst Larry Ceisler tells Axios.
• But the candidates bypassed the commission for the two debates this election following complaints about its format. The campaigns negotiated with TV networks themselves.

Zoom in: Trump and President Biden reached an agreement with ABC News to host one of the debates before Biden dropped out of the race.

• Harris maintained the agreement for Tuesday's debate.

Go deeper: What to know about the first Harris vs. Trump debate