WASHINGTON -- The final tallies in Monday's Iowa caucus showed a very narrow win for Hillary Clinton. But one demographic divide between the two candidates was not even close: Clinton is popular with older people. Millennials love Sen. Bernie Sanders (I-Vt.).

Entrance polls of caucusgoers show Clinton besting Sanders with voters over 45. They also show Sanders crushing Clinton with everyone else, including a 70-point margin among voters under 30. As Sarah Kliff at Vox notes, that's an even bigger slice of the Iowa youth vote than a senator from Illinois named Barack Obama took back in 2008 (he got 57 percent). Sanders also bested Clinton 58 to 37 among voters aged 30 to 44.

Today's Democratic Party isn't the same coalition that gave Bill Clinton the presidency in the 1990s. While Democrats at the time savored his electoral strength, the major elements of his governing legacy -- welfare reform, Wall Street deregulation and tough-on-crime criminal justice policies -- were Republican priorities.

Clinton supporters have long insisted that such "triangulation" with the GOP was essential to the Democratic Party remaining relevant in the post-Reagan era. But the financial crisis of 2008 and the Great Recession changed the political playing field. Today's Democratic base is far more skeptical of corporate power than the party of the 1990s was. A bipartisan consensus has emerged that Bill's GOP-backed crime bill fueled mass incarceration. Even conservative boosters of his welfare reform have acknowledged that it fails during the recessions, hurting the poor.

For older voters, the partisan fights of the 1980s and 1990s were formative political experiences. They see Hillary Clinton and the broader Democratic Party establishment as figures who survived relentless Republican attacks (which they did). But Sanders' massive 84 to 14 margin over Clinton among voters under 30 shows that the party's future is eager to break with its past. This is a wing of the party that wanted to see Sen. Elizabeth Warren (D-Mass.) run for president on an anti-Wall Street platform, which Sanders has adopted. It's a wing of the party that is uneasy with a candidate who served on Walmart's board of directors and made millions of dollars giving speeches to Wall Street, even after her family had amassed a nine-figure fortune.

It is, in short, the wing of the party whose worldview was shaped more by the banking crash than the Reagan era -- a generation angry about income inequality which does not trust the generation that created the problem to fix it.

Fortunately for Clinton, the younger a voter is, the less likely he or she is to vote. The polling data show that 37 percent of the electorate came from the under-45 demographic in Iowa, meaning that Clinton's 58 to 35 win over voters aged 45 to 64, and 69 to 26 win among voters over age 65, kept her in the contest.

In 2008, Clinton's biggest political obstacle was her vote for the Iraq War. Today, her candidacy epitomizes a problem for the entire Democratic Party establishment: How to appeal to an electorate whose political views were shaped by a Wall Street crash that left the elites in both parties largely unaffected. Sanders has figured it out.

Eight years ago, Clinton could at least console herself with the fact that she lost the youth vote to a younger candidate. On Monday, she lost it to a 74-year-old. That shouldn't frighten Democratic Party elites, since Sanders has shown them that even the elderly can be hip with the right platform -- going hard at Wall Street, corporate monopolies and campaign finance corruption works. Whether a party establishment built on corporate compromise is willing to make the adjustment, however, is a different question.

Zach Carter is a co-host of the HuffPost Politics podcast "So, That Happened." Subscribe here or listen to the latest episode below: