to help provide it with information, and members of Congress have staff and offices to assist them as well. In addition, a vast industry of lobbyists helps members write legislation on behalf of diverse corporate and labor interests. Committees Specializations The committee structure permits members of Congress to study a particular subject intensely. It is neither expected nor possible that a member be an expert on all subject areas before Congress. As time goes by, members develop expertise in particular subjects and their legal aspects. Committees investigate specialized subjects and advise the entire Congress about choices and trade-offs. The choice of specialty may be influenced by the member's constituency, important regional issues, prior background and experience. Senators often choose a different specialty from that of the other senator from their state to prevent overlap. Some committees specialize in running the business of other committees and exert a powerful influence over all legislation; for example, the House Ways and Means Committee has considerable influence over House affairs. Power Committees write legislation. While procedures, such as the House discharge petition process, can introduce bills to the House floor and effectively bypass committee input, they are exceedingly difficult to implement without committee action. Committees have power and have been called independent fiefdoms. Legislative, oversight, and internal administrative tasks are divided among about two hundred committees and subcommittees which gather information, evaluate alternatives, and identify problems. They propose solutions for consideration by the full chamber. In addition, they perform the function of oversight by monitoring the executive branch and investigating wrongdoing. Officer At the start of each two-year session, the House elects a speaker who does not normally preside over debates but serves as the majority party's leader. In the Senate, the vice president is the ex officio president of the Senate. In addition, the Senate elects an officer called the president pro tempore. Pro tempore means for the time being and this office is usually held by the most senior member of the Senate's majority party and customarily keeps this position until there is a change in party control. Accordingly, the Senate does not necessarily elect a new president pro tempore at the beginning of a new Congress. In the House and Senate, the actual presiding officer is generally a junior member of the majority party who is appointed so that new members become acquainted with the rules of the chamber. Support services