Before adoption of the Twenty-fifth Amendment
in 1967, there was no system in place to fill a vacancy in the vice presidency
. Whether the vacancy was due to a death, resignation, or succession to the presidency, the office remained vacant for the duration of that presidential term. In the 19th century, the Senate's President pro tempore
served as "acting vice president" during such absences, and it was common to refer to the President pro tempore — in this case Senator Benjamin Wade
of Ohio — as "vice president." Although the President pro tempore assumed many of the duties of the vice president under these circumstances, he was never allowed to exercise the vice president's constitutional duty to break a tie vote in the Senate.