The Senate foreign relations committee approved Hillary Clinton to become the next secretary of state on Thursday morning, as confirmation hearings began for Eric Holder (attorney general), Janet Napolitano (secretary of homeland security), and Ken Salazar (secretary of the interior). Wait—Obama isn't even president yet! How can the Senate be confirming his Cabinet officials already?

It's not. The term "confirmation hearing" is somewhat misleading—the committees that have been hearing testimony last week and this week aren't actually voting to install the candidates in the Cabinet: Rather, they're making recommendations to the rest of the Senate on whether those candidates should be confirmed when the appropriate time comes. It's a time-saving device so that President Obama can hit the ground running with a team of advisers as soon as possible.

In fact, nothing can become official until Obama first takes the oath of office Tuesday and then submits a message to Congress formally naming his Cabinet nominees. By that time, the Senate majority leader—who's in charge of the legislative calendar—will probably have already scheduled a floor vote for the entire chamber. (He can do so as soon as the committee that held the hearing submits its report.) A simple majority is needed to confirm a candidate, though opponents can filibuster. Majority Leader Harry Reid hasn't scheduled any votes yet, but his office says that it hopes to confirm "some nominees" on Inauguration Day.

It's not uncommon for lawmakers to get a head start on their deliberations. Technically, the Senate can begin hearings whenever it wants—it doesn't even have to wait for the electoral votes to be formally tallied. In the past, confirmation hearings have begun as early as December. Since Jimmy Carter, nearly every new president has had at least a handful of Cabinet members lined up and ready to go by Inauguration Day. In 2001, George W. Bush had seven Cabinet members approved (by the committees, at least) by the time he took office.

Usually, candidates are confirmed without too much controversy. In the 20^th century, only three Cabinet nominees were rejected by the Senate in its whole-chamber vote. In 1925, Charles B. Warren was turned down because of his close connections to a sugar conglomerate that had been investigated by Congress; the same fate befell Lewis Strauss in 1959, on account of his haughty attitude and unpopular policies as former chairman of the Atomic Energy Commission; and in 1989, John B. Tower was rejected for reasons ranging from reputed boozing and womanizing to unseemly ties to defense contractors. Warren and Strauss had both been approved by their respective committees—though Strauss by just a single vote—and Tower received an unfavorable report from his.

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Explainer thanks Betty Koed of the Senate Historical Office, the office of Sen. Harry Reid, and Steven S. Smith of Washington University in St. Louis.