MICHAEL BARONE: The Democratic majority that emerged — and disappeared.

John Judis, co-author of the book The Emerging Democratic Majority, now says in an article in National Journal that that majority has disappeared. His title: “The Emerging Republican Advantage.”

The original book, published in the Republican year of 2002, forecast accurately the groups that would make up the Democratic majority coalition that emerged in the 2006 and 2008 elections: blacks, Hispanics, gentry liberals, single women, young voters.

But as Judis writes now, that coalition has come apart. That’s partly because of diminished support from Millennials and Hispanics, but mostly because of additional white working-class defections and erosion among suburbanites unhappy with higher government spending and taxes.

In fact, he now says that the majority he predicted endured for only two elections. President Obama was re-elected with a reduced 51 percent of the vote, but Republicans won the House in 2010, 2012 and 2014, and the Senate in 2014. Democratic strength in governors’ mansions and state legislatures is at its lowest level since the 1920s. . . .

Even if they haven’t achieved permanent majorities, American parties have had enduring public policy successes. Social Security (passed 1935) and the Taft-Hartley labor law (passed 1947) are examples.

But it’s not clear the Obama Democrats accomplished that. The 2009 stimulus package’s steep increases in spending were cut back by the 2013 sequester. Tax increases may be pulled back. The administration has had to make dozens of revisions to the still-unpopular Obamacare and may have to accept serious rollbacks if it loses King v. Burwell in the Supreme Court in June.

Republicans looking to 2016 should be aiming not at creating a permanent partisan majority but at developing public policies that could, unlike Obama’s, be successful and enduring.

Well, I have a few ideas.