Source: "Free exchange: Left behind"
During the 1970's, rising inflation and unemployment convinced even Democrats that freer markets were the only way to guarantee growth. By 1992, the Democratic Party had abandoned its Big Government approach in favor of technocratic centrism - using education and mildly progressive taxation as a way to smooth off the rough edges of economic inequality.
In the 2000's, wage growth stalled as George Bush spent Clinton's budget surplus on tax cuts for the wealthy. Income inequality has continued to increase. The election of Trump has now liberated those on the left to abandon centrism for bolder approaches.
Senators Sanders and Warren talk of free college, reduced student debt and single-payer health care (which would allow people to leave jobs they loathe without losing health insurance, increasing worker power). Others like the Center for American Progress, have advocated for job guarantees in which the government would be the employer of last resort. Finally, there is universal basic income or UBI which would create efficiencies as it replaces the welfare bureaucracy with a single cash payment. It also solidifies the idea that everyone should benefit from economic growth.