When Christ was on Earth, he said to help the poor. He also said the poor will always be with us. Helping others is a universal obligation. It applies to Catholics, Jews, Protestants, Muslims and all others. In order to belong to any organization, club or entity, you must obey their rules and policies.
The Democratic platform is entirely opposite the church teachings and doctrine on abortion, gay marriage and stem cell research.
I believe the platform is the most anti-Catholic platform in the history of our country. Christ said, "You cannot serve two masters." Therefore, it is impossible to be a practicing Catholic and a Democrat regardless of how much you help the poor.
If you did, you would be a Cafeteria Catholic -- one who chooses what he wants to believe and what he does not.