Probably one of the hardest things for fans of Bernie Sanders to accept is that some Democrats actually like Hillary Clinton. Not just respect her, or think she is a more formidable candidate against Republicans, or are excited about a first female president, but genuinely like her. Certainly, that feeling is not universal. Bill Clinton is famously personable and personally charming, but when Barack Obama infamously told Hillary Clinton in the 2008 primary that she was "likable enough," many Democrats nodded in agreement.

In 2016, Clinton once again finds herself in a politically existential fight with a candidate who has captured the imagination and passions of a sizable slice of the Democratic base. She alluded to this in her closing statement in Thursday night's Democratic debate in New Hampshire. "I hear some talk that people are trying to decide, do they vote with their heart, do they vote with their head?" she said. "I'm asking you to bring both your heart and your head to vote with you on Tuesday, because we have a lot of work that can only come because your heart is moved."

As she had in her opening statement, Clinton tried to expand Sanders' focus on economic inequality to include discrimination based on race, gender, immigration status, or against members of the LGBT community. The MSNBC hosts hadn't picked up on those issues, and so Clinton spent much of the night fighting on Sanders' turf.

She acknowledged that many younger Democrats have already given their hearts to Sanders: "I have been moved by my heart ever since I was a young woman about the age of a lot of Sen. Sanders' supporters, worrying about what I could do to make a difference for my country, and I will bring that heart with me. But I will also tell you, we've got to get our heads together to come up with the best answers to solve the problems so that people can have real differences in their lives that will make them better."

Part of Clinton's problem is that Sanders is exceptionally easy to like and respect. He appears honest, authentic, and incorruptible at a time when mistrust of politicians and the political establishment is running hot. He looks and talks like a version of Larry David, or perhaps the Jewish grandfather from Brooklyn that most of us never had. He is, as someone once said, vinyl in a music-streaming world. Clinton is probably a CD.

Another problem is that Clinton is trying to wage the heart battle on issues of noneconomic inequality — racism, sexism, homophobia, Islamophobia — that ordinarily resonate with the Democratic base, and still do to some extent (Clinton leads Sanders by wide margins among black and Latino Democrats, so far). But lots of Americans are still (justifiably) angry over the 2008 financial crisis and the lack of jailed bankers, or still struggling financially after decades of accelerated income inequality. Donald Trump has tapped into a similar electoral vein on the conservative side.

According to psychologist Abraham Maslow's hierarchy of needs, people won't worry about their social status or sense of esteem until their physiological needs — food, clothing, shelter — are met. Voters who are unsure about how they are going to feed their family or pay for health care are perhaps unlikely to want to engage in a conversation about transgender rights.

But there's also something about Hillary Clinton. There are Democrats who absolutely love her, and loyally stuck with her in 2008 even when it was clear Obama was going to win the nomination. But there have also always been people who just don't like or trust Hillary, dating back to her first year as first lady in 1993. This election cycle, her weakest demographic is voters 30 and under — the millennials.

Catherine Rampell at The Washington Post writes that this age cohort is especially drawn to Sanders' socialism and ill-fitting, ruffled authenticity, but argues that this "form of authenticity is off-limits to to any female politician," especially Clinton. "Female politicians — at least if they want to be taken seriously on a national stage — cannot be unkempt and unfiltered, hair mussed and voice raised," she says. "They can't be too quiet or too loud, too emotional or too cold, too meek or too aggressive, and so on. But they also can't appear to be trying too hard."

Rampell's Washington Post colleague Dana Milbank notes that sexism "is difficult to prove" in the Clinton-Sanders matchup. "But there does seem to be a long-running game in which Clinton can never quite meet the expectations set for her, even if her actual achievements are considerable," he says. "Clinton, to her credit, is not pretending to be something other than herself this time," Milbank adds, noting that her "less-than-soaring pitch" is that she has deep experience and can get things done.

It's hard to tell at this point whether Clinton or Sanders is more in step with the Democratic Party, much less the country. Iowa and New Hampshire aren't necessarily great thermometers to gauge the temperature of the generally more diverse, temperate 48 other states. The Democratic primary will ultimately reveal whether the party wants the consummate Democratic political insider or the longtime independent who has energized the grassroots. (Sanders' biggest laugh on Thursday night was when he said he wasn't the spoiler in a three-way race he lost to a Republican; the third-placing Democrat was the spoiler.)

One of the two — Clinton or Sanders — will win the nomination, and neither can afford to alienate the other's supporters. On most issues — the death penalty and health care are exceptions — they agreed on policy and even how to implement it. But the stylistic differences matter. Clinton's overt pitch on Thursday night was a play for the head: Sanders is making promises he can't keep, and she has the experience and ability to make real progress on issues Democrats care about. Sanders, as always, stirred the heart and appealed to a sense of justice and outrage at a fixed, corrupt system.

If Clinton can find a way to worm her way into the hearts of young liberal Democrats, Sanders is in trouble. Conversely, if Sanders can convince Democrats outside his base of support that he can beat Marco Rubio or Donald Trump or Ted Cruz and then get stuff done in Washington, Clinton is in trouble.

If the party remains fractured, there are cautionary tales for Democrats on both sides, as there always are in politics. In 1972, Democrats went with their hearts, and George McGovern was destroyed by Richard Nixon. Hillary Clinton says she can unite the Democratic Party behind her. Maybe that's more important than earning the love of its liberal base. But her job will surely be easier if she can, as Tracy Chapman sings, find the right words, at the right time, to win their hearts.

Editor's note: A previous version of this article misidentified Nixon's opponent. It has since been corrected. We regret the error.