Voting in the Senate is the ultimate step in the legislative process. When a bill is passed by the Senate and the House of Representatives, it is sent to the president for his signature. He can sign the bill into law or veto it. If vetoed, the bill is sent back to the chamber of origination. Congress can overturn a presidential veto with a two-thirds majority in both houses.
There are three ways of voting in the Senate:
A roll call vote occurs when each senator votes "Yea" or "Nay" as his or her name is called by the clerk, who records the votes on a tally sheet. A roll call vote must be taken if requested by one-fifth of a quorum of senators. Typically, a simple majority is required for a measure to pass. In the case of a tie, the vice president (president of the Senate) casts the tie breaking vote. An affirmative vote of three-fifths of the senators duly chosen and sworn is typically required to invoke cloture. To invoke cloture on a change in Senate rules, a two-thirds vote is required.
In a few instances, the Constitution requires a two-thirds vote of the Senate, including: expelling a senator; overriding a presidential veto; adopting a proposed constitutional amendment; convicting an impeached official; and consenting to ratification of a treaty.
A voice vote occurs when the presiding officer states the question, then asks those in favor to say "yea" and those against to say "no." The presiding officer announces the results according to his or her best judgment. In a voice vote, the names of the senators and the tally of votes are not recorded.
The least common vote in the Senate is a division (or standing) vote. If a senator is in doubt about the outcome of a voice vote, he or she may request a division vote, whereby the presiding officer counts the senators voting yea and those voting no, to confirm the voice vote.
The outcome of Senate votes are printed in the Congressional Record. The Senate's roll call votes from the 101st Congress to present are available online. Roll call votes are also now available in XML.