I know it doesn't help when liberal/progressive religious groups are ignored or even attacked by those with whom they share political ideology. The press also ignores these groups - just not sexy enough.
There is no doubt that the religious right has out shouted the left, but I see that pendulum swinging.
There have been some vocal leaders. Gene Robinson, Sister Simone Campbell. You are not likely to see much of them, except on Bill Moyers and the like. Bill Moyers is another good example of an extremely vocal leader who makes no secret of his religiosity. There was a whole coalition of Catholic clergy who spoke loudly against the Ryan budget. And then, of course, there is the President and Vice President.
Because those on the left don't really practice "prosperity gospel", as those on the right due, resources are much more scarce.
The key seems to me to be in coalition building. That's why I support both religious and secular groups who support and fight for the causes I believe in.