When I was very young, before I was a Catholic, I remember people talking about how you would know when a new Pope had been elected. Here's a wonderful misconception for you. The person explaining said that after the Cardinals voted they burned the ballots and if the smoke that came out of chimney was black, they had to vote again, and if it was white then the Holy Spirit had chosen a Pope. Both he and I were under the impression that the Holy Spirit changed the color of the smoke "on the fly" as it were. Nice if true, but alas, the reality is much more mundane.
The scenario sounds like that section of the Talmud where the scarlet ribbon of the scapegoat always used to turn white on Yom Kippur, but stopped turning white after the death of Jesus...
Here's a discussion of it
It would be so much easier if God made the choice outright... that free choice thing's always getting in the way. :)
Of course, only one problem with it if it were the way: who would tell the Cardinals what color smoke came out?