Demography is destiny, dear boy. That’s the central argument in the popular book authored by John Judis and Ruy Teixeira, The Emerging Democratic Majority. Their thesis held that the Democratic Party would enjoy decades of dominance as the “coalition of the ascendant” – unmarried women, young people, and minority voters – overtook the white majority. That hypothesis enjoyed some confirmation in the form of the presidential election results in 2008 and 2012, but it has since come under intense scrutiny. Even one of EDM’s authors has begun to critically revisit his theory.

“After the 2008 election, I thought Obama could create an enduring Democratic majority by responding aggressively to the Great Recession in the same way that Franklin Roosevelt had responded in 1933 to the Great Depression,” Judis wrote. “Obama, I believed, would finally bury the Reagan Republican majority of 1980 and inaugurate a new period of Democratic domination.”

“In retrospect, that analogy was clearly flawed,” he conceded.

The interruption of Hillary Clinton’s coronation by the impertinent socialist Sen. Bernie Sanders (I-VT) has led some observers to again take a critical look at the Democratic coalition. Writing in The New York Times on Thursday, Nate Cohn noted that the Democratic Party is generally happy with simply handing Clinton the nomination. While the liberal commentary class is starving for a competitive primary, the polls indicate that the average Democratic voter is not.

That might seem somewhat surprising if you’re an affluent, secular, well-educated person living along the coasts, in places like Bethesda, Md., Berkeley, Calif., or Montclair, N.J., where the party really is dominated by the uniformly liberal voters who love Elizabeth Warren and harbor at least some reservations about Mrs. Clinton. From that vantage point — which happens to be the same as that of many political journalists — it often looks as if Mrs. Warren could even defeat Mrs. Clinton.

But the Democratic primary electorate is nothing like these liberal enclaves. Elsewhere, the party includes a large number of less educated, more religious — often older, Southern or nonwhite — voters who are far from uniformly liberal.

The majority of Democrats and Democratic primary voters are self-described moderates or even conservatives, according to an Upshot analysis of Pew survey data and exit polls from the 2008 Democratic primary.

Cohn’s demographic analysis of the leftward orientation of various aspects of the Democratic coalition is revealing. He noted that, despite their reliable support for Democratic candidates, the members of the “coalition of the ascendant” are among the least dogmatically progressive Obama voters.

Cohn found that African-American and Hispanic voters are generally moderate Democrats. “Many black voters are moderate or conservative, allowing Mr. Obama to overcome the disadvantage faced by left-liberal Democratic candidates,” Cohn wrote. That’s a … debatable assertion, to say the least. But it is interesting to note that minority Democratic voters are less attracted to the party’s platform than previously believed.