Attendance
The Constitution specifies that a majority of members constitutes
a quorum to do business in each house. Representatives and
senators rarely force the presence of a quorum by demanding quorum
calls; thus, in most cases, debates continue even if a majority is
not present.
The Senate uses roll-call votes; a clerk calls out the names of
all the senators, each senator stating "aye" or "no" when his or
her name is announced. The House reserves roll-call votes for the
most formal matters, as a roll-call of all 435 representatives
takes quite some time; normally, members vote by electronic
device. In the case of a tie, the motion in question fails. In the
Senate, the Vice President may (if present) cast the tiebreaking
vote.