The Pope is in Mexico today to make a 16th-century Nahuatl into the continent's first indigenous saint.
It is part of a strategy to stem the advance of evangelical sects among the poor and downtrodden descendants of the first Latin American converts to Catholicism.
But behind the enthusiasm generated by the ailing Pope's determination to drag himself to Mexico, there are several bitter controversies surrounding soon-to-be Saint Juan Diego and his visions of the dark-skinned Virgin of Guadalupe in 1531. These include the long-running debate on whether he actually existed, and a more recent dispute about the colour and bushiness of his beard, if he did.
The canonisation is the highlight of a two-day papal visit which began yesterday.
The police estimate that by the time the Pope leaves for Rome on Thursday more than 12 million people will have lined the streets for a glimpse of the Popemobile.
About 1.5 million people are expected in the vicinity of the Basilica of Guadalupe, where the mass will be held before a select congregation of 20,000.
The basilica stands where Juan Diego saw the Madonna, and is the centre of his steadily growing cult, encouraged by the church in its effort to display a new sensitivity towards Mexico's 10 million indigenous people.
In the streets outside merchants peddle a range of outrageously gaudy Juan Diego statues, pictures, and trinkets.
Earlier yesterday the Pope was in Guatemala, where thousands of young people walked from an all-night vigil to a racetrack for a canonisation mass for Pedro de San Jose Betancur, a 17th-century Spanish missionary who dedicated his life to helping the poor. They spent the night waving candles and chanting.
Intent on injecting new vigour into the flagging calender of saints as a means of strengthening popular faith, John Paul has created more than 450 saints since he became pope in 1978.
Juan Diego is a prime example of his quest to recognise popular heroes.
The Virgin's appearances just 10 years after the Spanish conquest not only played a key role in converting Mexico during colonial rule, but remains at the heart of modern Mexican Catholicism.
The expectation is that raising the status of the native American usually pictured trembling at the Virgin's feet could help stem a worrying exodus from the church of indigenous people and other disadvantaged groups who feel it undervalues them.
But beneath the surface of the canonisation euphoria there is a collection of complicated disputes. The most fundamental is the question of Juan Diego's existence.
It last flared in January in letter from a group of Mexican churchmen asking the Pope not to canonise "a myth" not mentioned in official texts until almost a century after the visions.
And with canonisation a done deal there is a new disagreement about what the indigenous saint should look like.
It began with the official portrait: a tall, white-skinned and heavily bearded Juan Diego looking more like a European missionary than an Nahuatl visionary.
This prompted a flurry of alternative darker, less hairy images, none of which has taken root, in part because it is also disputed whether Juan Diego was a peasant or a nobleman.
