The Cardinal is a historically significant film because of what was happening in the Roman Catholic Church at the time it premiered -- the Second Vatican Council. Called by Pope John XXVIII to bring about reforms in the Church, many of the issues touched upon in the film -- the liturgy, the role of lay persons and women in the Church, rights of the mother vs. the child, mixed marriage, ecumenism -- were being hotly debated by the bishops in Rome. The film added to that debate among ordinary Catholics.
I was a student at a Catholic high school in 1963. To many of us who hoped to see significant and even radical changes toward a more modern Church, the Cardinal dramatized many of the problems that we believed needed correcting. The Second Vatican Council didn't go as far as some of us would like, and the Church hasn't seen much reform since, but when I see the Cardinal today, I'm reminded how much more confining Church doctrine was before the Council did its work.
By the way, in response to the comment that no one could have done all the things that the Cardinal was portrayed as doing in the film, my understanding is that the story is based on the life of Cardinal Spellman of New York. The details are changed, but in fact Cardinal Spellman was from Boston and did undertake many of the same roles in his career, including working as a Vatican diplomat from 1925-1932.
