The Iowa caucuses reward enthusiasm, especially at the end. The famous three-step strategy that every campaign attempts to implement was popularized by former congressman Dave Nagle and is often summarized as: Organize, organize, and get hot at the end. In the final weekend of every caucus I have covered, the “hot” candidates were apparent from their final events.

You could see John Kerry’s events swell in 2004 as he rose from the low single digits in December to victory in January. In 2008, the late surges of Barack Obama, who won, and John Edwards, who zipped past Hillary Clinton, were visible in their final crowds. On the Republican side, the same was true for caucus winner Rick Santorum in 2012. (To my memory at least, this phenomenon was less obvious in 2016 when Ted Cruz beat Donald Trump and Hillary Clinton just barely defeated Sanders.)

This year it’s a little hazier. Each campaign has a kind of enthusiasm engine that needs fuel if it’s going to zoom across the finish line ahead of expectations in the final lap. All the campaigns know that beating Donald Trump is what consistently polls as the top concern for Democratic voters, and in their closing arguments each has crafted an electability argument that they are stressing.

Sanders and Biden both say they can win blue-collar workers that Clinton lost to Trump. Warren pitches her more-ambitious-than-Biden-but-not-as-radical-as-Bernie agenda as the key to both exciting and uniting Democrats. Buttigieg, pointing to Bill Clinton and Barack Obama, argues that Democrats only win when they nominate a fresh candidate of generational change.

But what creates real enthusiasm in each campaign isn’t electability. There’s another layer, deeper and more molten, that drives the activist cores of these campaigns and — especially in this historically unique field — it’s these sometimes hidden layers that may determine Monday’s results.

There’s a lot that’s not often conveyed in campaign coverage but that can be felt deeply on the ground. The conventions of the news business can often be limiting in this regard. What is generally considered campaign news is swings in polls, juicy quotes from surrogates, candidate gaffes, internal staff drama, policy fights, etc. What we are covering when we are at a campaign speech or rally is mostly theater: there’s a stage and a performer and an audience. And the artifice that goes into these productions can create a lot of cynicism, which is mostly healthy and is necessary for accountability journalism.

But I was frequently stuck this week by how easy it is to lose sight of the history that can unfold in front of us at these staged events. There are small moments at every candidate stop that smack you in the face about how consequential this primary is. And it’s in these moments that you can detect that molten layer, the one that isn’t just about a bloodless electability argument, that drives voters to be passionate about their candidate.

In Iowa City on Saturday a little girl named Prudence, with the help of her mom, asked Warren why she decided to run for president. Warren’s answer wasn’t particularly newsworthy. In fact, she reverted to some of the biographical talking points in her stump speech (she always wanted to be a teacher but a mid-career curiosity about the iniquities of bankruptcy set her on a winding path to elective office). But the moment captured what fuels the engine of Warrenism for so many of her supporters: the unfinished business of female equality in America. Corruption is Warren’s closing argument, a message that has wide appeal, but the activist fuel comes from supporters, women and men, who want Prudence to grow up without thinking twice about running for president.

Later that night, at a big Sanders rally and concert in Cedar Rapids, Cornel West, the activist and intellectual, made a notable comment to the 3,000 attendees in the arena. “I’ve been waiting 50 years for a movement like this,” he said. Like Sanders, West is a longtime soldier of the old left, the one that grew out of the ’60s, never accommodated itself to the rise of Reaganism in the ‘80s and the New Democrats in the ’90s. Sanders has wedded this movement, which has survived on the fringes of Democratic politics for decades and was thought to be dormant, to a new wave of leftism anchored in the millennial generation that was shaped by the traumas of post-9/11 wars and the Great Recession.

It is still a minority in Congress and the Democratic party but it has young charismatic elected leaders, like Alexandria Ocasio-Cortez, Rashida Tlaib, and Ilhan Omar, all women of color who have generated massive enthusiasm stumping for Sanders in Iowa. Watching a great Vampire Weekend or Bon Iver concert can mask the fact that what is stirring in Iowa with the Sanders campaign could be the takeover of the Democratic Party by this faction. At the very least, it is the start of an enormous battle that will unfold over the next few months.

It is at the Biden events where you have to sniff hard to smell the gasoline that drives his candidacy. His is a pure electability candidacy, and while polls show that’s what the people want, it can seem hollow.

His surrogates are older former Democratic senators like John Kerry, Bob Kerrey, and Chris Dodd. They may have had roots in the left of the ’60s, but all responded to the rise of the right by fashioning a Democratic politics that is often defined, for perfectly defensible political reasons, by ensuring that they don’t provoke a massive backlash from the right. That’s how Bill Clinton won, and while he updated Clintonism, Barack Obama governed in the same way and has warned Democrats to do the same this year. That negative progressivism — warning about going too far left rather than proudly championing your own bold agenda — leaves Biden relying solely on Democratic voters’ hatred of Trump.

Considering that Biden has led in national polls for almost the entire race, that has seemed like a good bet. But in Iowa, it may leave voters wanting something more inspirational, and if so they have plenty of other options.