Which vice president cast the most tie-breaking votes in the U.S. Senate? How many?
Article I, Section 3 of the U.S. Constitution, establishes the vice president as president of the Senate but stipulates that he/she can only vote when the Senate votes are "equally divided."
According to the Senate's official web site, Adams' votes protected things like the president's sole authority over the removal of appointees, the location of the national capital, and once prevented war with Great Britain.
Adams scholars have since discovered evidence that he may have filed as many as 31 tie-breaking votes, but the Senate Historical Office has only been able to document 29.
The next closest vote total was compiled by James K. Polk's second-hand man, George Mifflin Dallas. A self-proclaimed fame-chaser, Dallas claimed triumphantly that he cast 30 tie-breaking votes during his four years as president of the Senate. However, the Senate Historical Office could only document 19 votes, which is still good enough for second on the list.
—The Fact Monster