The growing class gap is between the married middle class and the cohabiting working class and poor people. One of the reasons the bottom half of the class structure is getting less likely to marry is that they think you already have to be steadily middle class first. Brad Wilcox and Andrew Cherlin present the latest numbers in a useful Wall Street Journal article.
The future success stories among the poor and working class who grow into the middle class will, I am confident, be mostly told by those who make the commitment to marriage (and religion) the foundation of their lives. With that strong foundation, building, saving, and investing in the family is easier and safer.
The best thing we can do for the working poor and working class is to promote the idea that a permanent commitment to marriage (and not just to your spouse) will help you make a richer and more secure life for yourself and your children.