Public political bodies are by their nature evolving creatures that set their own policies and procedures. Often the bodies agree to be governed by "Robert's Rules of Order," a set of protocols first published in 1876 by Robert Martyn Robert after he encountered parliamentary chaos in public bodies during his travels around the United States as a military officer. Mastery of parliamentary rules has added to the power of many rising and veteran politicians and can make the difference between success and failure for legislation. At the national level controversy continues to swirl around the cloture rule in the U.S. Senate. Cloture is a procedure used to stop a filibuster, the method politicians can use to delay a vote or block debate on a bill often by talking at length without yielding the floor. Historically it took a two-thirds vote of the Senate to "invoke cloture," that is to end a filibuster and proceed. In 1975 that vote was reduced to a three-fifths vote, that is 60 of the 100 senators. That is why 60 has become the magic number for Democrats currently in control of the Senate by a small majority when it comes to advancing legislation. While some advocate banning the filibuster as an unconstitutional relic, others argue it protects the minority party against oppression by the majority.