In current practice, the threat of filibuster is more important than its use; almost any motion that does not have the support of three-fifths of the Senate effectively fails. This means that 41 senators can make a filibuster happen. Historically, cloture has rarely been invoked because bipartisan support is usually necessary to obtain the required supermajority, so a bill that already has bipartisan support is rarely subject to threats of filibuster.