I've suggested a couple of reasons why attempts by the Democratic Party to appeal to Christians on the basis of a shared humanitarian social and economic agenda may not bare fruit. One, the social gospel ranks below the issue of debating whether God exists or not and whether He created the world. Two, today's U.S. Christians are basically materialistic and don't really take the New Testament and its teachings that literally at least to the extent that it would threaten their lifestyle and material aspirations.
A third reason is that the Christian Right's agenda and its following is stimulated by what one of my fellow bloggers (sorry, can't remember where I read this) has identified as an "outrage" quotient (my paraphrase). Terri Schiavo, Ten Commandments, school prayer, abortion, gays, Christian Nation, etc, are all issues that are designed to provoke outrage and fear on the part of the Christian community that they and their existence is threatened by the Secular Left and liberal democratic institutions (see the recent hysteria about the courts). Trying to appeal to most Christians' compassion for others simply doesn't generate the same level of outrage, if it provokes any outrage or concern at all. In the case of corporate abuses, most Christians are not conditioned to see this as a threat against Christianity or themselves, while considerably less substantive issues, like school prayer, do seem more like a threat, and are so framed by members of the religious elite to stoke up their congregants' resentment that they--Christians--are under seige. The need to help the poor doesn't provoke the same kind of reaction.
And among many Christians, there is a not uncommon view that at least in the U.S., the Poor aren't really "poor". And compared to the poor of other countries, there's some truth to this view.
But in any event, the conservative symbolic issues that have gained traction among Christians have done so because of their ability to provoke fear on the part of Christians that they can't or soon won't be free to practice their religious beliefs. As a Christian myself, I don't share these fears, and I think the Christian Right's attempts to manipulate church goers this way takes advantage of our relative ignorance of political issues and our naturally inclined self centeredness and desire for self preservation.
So, unfortunately, I suspect appeals to U.S. religious identifiers on the basis of a more humanitarian gospel will not have a great impact. But I'm willing to be convinced wrong.