Thousands of Trump supporters — many chanting "Hang Mike Pence" — marched on the Capitol on Jan. 6, 2021, as Pence met with lawmakers for what is normally a routine ceremony to certify the election.
The answer is quite simple: it's in the U.S. Constitution. "The Vice President of the United States shall be President of the Senate, but shall have no Vote, unless they be equally divided" (Article I, section 3).
