There’s a new divide in the Democratic Party. It’s a divide as much about age as ideology. While older voters clearly support the presidential ambitions of former Secretary of State Hillary Clinton, the younger generation is firmly in favor of her rival, Sen. Bernie Sanders. Anyone who wants to fully grasp the changes roiling the party today must pay close attention.

Younger Democrats came of age during a time of blossoming liberalism in America. According to a recent Gallup poll, more Americans self-identify as liberal today than at any time since 1992. Among young Americans, socialism, the ideological label Sanders uses to describe himself, polls about as well as capitalism. While it has been long accepted that people grow more conservative with age, recent research calls this truism into question.

According to political scientists Yair Ghitza and Andrew Gellman, our political views form primarily from the ages of 14 to 24 and become more stable with time. This explains why the rise of the modern conservative movement in the 1980s under President Ronald Reagan still shapes our politics today.

In 1988, The New York Times noted that only 20 percent of voters ages 18 to 29 identified as Republican eight years earlier. By 1988, however, 33 percent of those voters (by then age 26 to 37) were members of the Republican Party. As the conservative writer David Frum noted in 2008, “The 20-somethings of the 1980s remain the most Republican cohort in the electorate to this day.”

Baby boomer Democrats came of age within this context and, understandably, internalized its lessons. Voters who were children or teenagers during the liberal optimism of the 1960s Great Society reached adulthood at the same time as a historic rightward political shift. The Democratic Party ignored and downplayed this sea change, and — apart from the interregnum when President Gerald Ford, a weak successor to Richard Nixon, lost re-election to Jimmy Carter — the party was punished with sound defeat in election after election. Only when it finally came to terms with this shift and moderated its platform accordingly was it able to secure electoral victories, starting with Bill Clinton’s first presidential win in 1992.

The ideological battle waging among Democratic voters is a conflict that reaches back over 30 years, and yet the two sides’ competing visions have rarely been this distinct. Whether it was Barack Obama versus Hillary Clinton, Howard Dean versus John Kerry or Jesse Jackson versus Michael Dukakis, the ideological separation has remained remarkably stable through recent decades. How one views this divide is likely as much a function of life experience as of ideological preference. How else to account for the huge generational gap separating Clinton’s supporters from Sanders’?

In early Democratic primaries, Clinton has fared best among voters older than 65, a voting bloc that still remembers the embarrassing losses the Democrats faced after their midcentury electoral dominance. A humbling string of defeats profoundly transformed the Democrats’ conception of the American electorate. The failures are well documented: George McGovern, hero of the liberal wing of the party, was soundly defeated by Richard Nixon in 1972. Carter won the 1976 election, but in doing so forged an ignominious legacy that probably did the party more harm than good.