From accuracy.org:
— “Televised Joint Appearances”: In 1985, the national chairs of the Democratic and Republican parties, Paul Kirk and Frank Fahrenkopf, signed a remarkable agreement that referred to future debates as “nationally televised joint appearances conducted between the presidential and vice-presidential nominees of the two major political parties … It is our conclusion that future joint appearances should be principally and jointly sponsored and conducted by the Republican and Democratic Committees.”
— “Exclude Third-Party Candidates”: In February 1987, Democratic Party chair Kirk and GOP chair Fahrenkopf together issued a press release and held a D.C. news conference to announce the formation of the Commission on Presidential Debates (“Commission on Joint Appearances” apparently didn’t sound right) — with themselves as co-chairs. The press release called the new group “bipartisan.” According to the New York Times, Fahrenkopf indicated at the news conference that the CPD was “not likely to look with favor on including third-party candidates in the debates.” The Times reported: “Mr. Kirk was less equivocal, saying he personally believed the panel should exclude third party candidates from the debates.” The newspaper quoted Kirk: “As a party chairman, it’s my responsibility to strengthen the two-party system.”