What limits the Religious Left is the fact the Democratic Party and the post-modern Left are overwhelmingly secularists composed of agnostics, skeptics, atheists and people indifferent to religion. These people abhor God Talk. And you think they want to hear it from like minded people who do believe in God any more than they want to hear it from their opponents on the Right? The Religious Left is up against a mindset hostile to even the idea of spiritual transformation. And their accomodation with the powers that be also limits their broader societal acceptance as well in that Religion does not rest easy with social licentiousness. Mainline's religion's embrace of it has led to a steady sustained decline in both its membership and its ability to spread its message. Its not a good time to be a religious liberal - a phrase that perhaps can best described as the 21st Century's classic oxymoron.
(Denny Crane: "Sometimes you can only look for answers from God and failing that... and Fox News".)