The group the elects a new pope is the College of Cardinals. Originally the Bishop of Rome was elected like all bishops: through votes cast by local priests and citizens. This changed for good in 1059 when Pope Nicholas II restricted the vote to just the cardinals a group which had been created only recently.
In Catholicism, cardinal is an ecclesiastical office and title. Originally cardinals were clergy who personally advised the pope; today the position of cardinal ranks above all other prelates (including bishops). The chief functions of the cardinals include the election of a pope (since 1059) and, thereafter, advising and helping him govern the church.
The college of cardinals is not an institution or higher learning or any sort of school. Here, college simply refers to a body of people who have a common purpose and shared duties. The college of cardinals is, then, just the association of cardinals in the Catholic Church.
There are currently 183 cardinals, of whom 117 are under 80 years old and therefore eligible to vote for the pope. Just three of them werent appointed by Pope John Paul II, a fact which many observers believe will be one of his lasting legacies.
There are three classes of cardinals: Cardinal bishops who are the bishops of the seven suburbs of Rome, Cardinal priests who oversee the dioceses in major metroplitan areas around the world, and Cardinal deacons who are priests serving administrative functions within the curia. The differences between the degrees of cardinal have little practical significance and stems from the fact that in 12th century the cardinals consisted of 7 bishops of dioceses around Rome, 28 priests from various Roman churches, and 20 deacons. Since 1962, all cardinals have been required to be bishops before being made cardinal.
In order to preserve links with tradition, each cardinal (no matter where he comes from) is made a nominal pastor of some church in the city of Rome. Only after taking possession of a church is one officially regarded as a cardinal. Whenever visiting Rome, they are expected to take time to minister to their congregation. Some cardinals are also made bishops (in name only) of suburbicarian sees surrounding Rome.
College of Cardinals
For a long time the college of cardinals was comprised almost entirely of Italian clergymen who knew each other well and who wanted to keep their numbers small in order not to dilute their considerable power. In 1586 Pope Sixtus V officially restricted the number of cardinals at seventy, a limit not exceeded until Pope John XXIII in 1958.
Other important changes were made by Pope Paul VI. In his Apostolic Constitution Romano Pontifici Eligendo, promulgated on October 1, 1975, he excluded from voting all cardinals over 80 years old. Because many cardinals were quite old, this was a controversial step, but the college of cardinals has accepted it.
Most important about this change was that it introduced the idea that the office of cardinal did not give one the automatic right to participate in the election of a new pope. This outraged many cardinals at the time; at some point in the future, it could be used as a basis for further changes by again allowing non-cardinals to vote for pope.
One question raised by this decision was whether a pope who reached the age of eighty needed to step down after all, if over-eighties could not be entrusted with the power to elect a pope, how could they be entrusted with the power of a pope? This is a legitimate question which has not been entirely answered, except perhaps to say that limiting the power of the cardinals was pragmatic, political move which need not be made when it comes to the papacy. This is a legitimate argument, but it underscores the fact that the choice of pope is as much political as it is religious, something which defenders of orthodoxy dont like to admit publicly.
Pope Paul VI also limited the number of voting cardinals to 120, a limit adhered to by Pope John Paul II until 2001 when he brought the total eligible to vote to 137. John Paul II has, in fact, appointed a tremendous number of bishops, archbishops, and cardinals, thus helping to ensure that those responsible for the election of his successors will be close to him on theological issues.
Today some question this central role of cardinals because there is no scriptural foundation for their existence. They are a medieval creation entrusted with the election of the head of the Catholic Church; for many, this is an unacceptable anomaly.
They argue that the election of the pope should rightly fall to the bishops or to whomever the bishops choose as their representatives (for example, the presidents of episocopal conferences). The reforms made by Pope Paul VI were, perhaps, a first step towards reforming the election of popes; eventually, their role may be diluted if not eliminated. Currently, though, it is a thousand-year-old tradtion that wont be set aside lightly.