They should also get firmly behind campaign finance reforms that limit the ability of big business and Wall Street to corrupt the political process.
Lesson Three: Democrats Need the White Male Working Class, and the White Male Working Class Should Need the Democrats
To create an enduring coalition, Democrats also need the white working class. They used to have it. In 1960, 57 percent of blue-collar whites identified themselves as Democrats, and only 26 percent as Republicans.
But that support began to erode dramatically. By 1980, 57 percent of the white working class voted for Reagan over Carter; in 1984, 65 percent backed Reagan over Mondale; in 1988 60 percent voted for Bush over Dukakis. And even though Bill Clinton managed to win back white working-class women, the shift of white men to the GOP continued.
It's tempting to point to race as the major contributor. To be sure, southern whites began deserting the Democratic Party after the Civil Rights Act of 1964. And the GOP has lost no opportunity to play the race card -- whether in the "Willie Horton" ads of 1988, or the more subtle racial message of "state's rights" in 2012.
But that explanation leaves out the bigger story.
The wages of white men without college degrees began falling in the late 1970s because of globalization and technological changes that corporations were all too eager to take advantage of.
Today, the typical white male worker without a college degree earns less than he did 35 years ago, adjusted for inflation.
Yet the Democratic Party has done little to reverse this trend. (It pains me to level this charge because I was Secretary of Labor in the 1990s and didn't fight hard enough.)
Democrats could have enacted labor law reforms that made it easier to form and preserve labor unions -- which in the 1950s and 1960s gave the working class bargaining power to get a fair share of the profits. Democrats could have pushed for a nationwide system of productivity bargains, as in Germany, through which employees get a share of the gains from productivity growth.
They could have insisted all trade-opening treaties require that America's trading partners have a minimum wage equal to half their median wage -- and have set America's own minimum wage to this standard. And Democrats could have reduced taxes on the middle and working class, and raised them on the rich.
By turning its back on white working-class men, the Democratic Party created a political vacuum Republicans have been all too eager to fill.
Whether through racism, xenophobia, or homophobia, or by means of right-wing evangelical Protestantism, the GOP have found scapegoats. Blacks, immigrants, gays, and women seeking abortions aren't responsible for the declining real wages of white men without college degrees, of course, but they are convenient targets of their anger.
The overall lesson is simple, and Democrats used to know it. As Harry Truman put it in 1948, we need a government "that will work in the interests of the common people and not in the interests of the men who have all the money."
That lesson needs to be relearned.