Senator Birch Bayh (Kefauver's successor as Chairman of the Subcommittee on Constitutional Amendments) proposed in the Senate and Representative Emanuel Celler (Chairman of the House Judiciary Committee) proposed in the House of Representatives what would become the Twenty-fifth Amendment. Their proposal specified the process by which a President could be declared disabled, thereby making the Vice President an Acting President, and by which he could regain the powers of that office.
Also, their proposal provided a way to fill a vacancy in the office of Vice President before the next presidential election. This was as opposed to the Keating-Kefauver proposal, which did not provide for filling a vacancy in the office of Vice President prior to the next presidential election or itself provide a process for determining presidential disability. In 1964, the American Bar Association endorsed the type of proposal which Bayh and Celler advocated. And that is where the 25th Amendment comes from.