As Catholic cardinals prepare for Tuesday's conclave to choose a pope, predictions run the gamut.

That wasn't the case in 2005, when one man was universally cited by news reports as the top contender: a conservative German cardinal, Joseph Ratzinger, the Vatican's longtime doctrinal watchdog. His aggressive orthodoxy had earned him the nickname "God's Rottweiler."

As now, 115 cardinals were eligible to vote in an election decided by a two-thirds majority. After just two days, white smoke spewed from a chimney, signaling that a pope had been chosen and making it the shortest conclave in 100 years.

Ratzinger, 78, soon emerged on the balcony over St. Peter's Square as Benedict XVI. Eight years later, he became the first pope in 600 years to retire.

Predicting popes isn't like predicting a president. Cardinals don't discuss their favorites or campaign for office. Predictions are educated guesses.

U.S. cardinals stopped holding news conferences in Rome after complaints from other cardinals. Until the conclave ends, the entire College of Cardinals is cut off from the press.

What happens in the conclave is supposed to be secret, a challenge in the digital age. The Vatican's sensitivity is high because of last year's "Vatileaks" scandal, in which private documents were leaked to journalists by Pope Benedict's butler. Extra security, from detecting bugging devices to blocking high-tech eavesdroppers, are in place.

The next pope is anyone's guess. In a "Sweet Sistine" tournament on the Religion News Service website, which invites anyone to vote, the finalists are cardinals from Canada, Brazil, Italy or Nigeria.

But Catholics believe the Holy Spirit guides the decision. As a sign of the times, some will await the outcome the traditional way: watching for puffs of white smoke from a Vatican chimney. Others might simply turn to Twitter and follow @PapalSmokeStack.

-------

Susan Hogan is a Star Tribune editorial writer.