Money isn't as decisive as some people think. Tends to buy apathy not action, and to matter less when voters pay attention. (Like my idea that ads mostly work when people have little opinion anyway.) Big issues have money on both sides, stalemating. Lobbying is often providing information (fight by having better paid staffers) and, ahem, votes. Leftism is hampered by structural problems (gerrymandering, the Senate) and the actual conservatism of many Americans.
http://www.vox.com/2016/2/9/10941690/campaign-finance-left
http://www.vox.com/2016/2/9/10941690/campaign-finance-left