Bernie Sanders has always hated personal attacks in politics. And the latest controversy surrounding his campaign shows why that's a particularly risky strategy when it comes to Hillary Clinton, whose supporters will always be poised to hit back. 

In an off-the-cuff remark to Bloomberg, Sanders's campaign manager Jeff Weaver joked that Sanders would be “be willing to consider” Clinton for vice president. “We’ll even interview her,” he added, the point appearing to be that Clinton is so heavily the favorite that the very idea sounds absurd. But the remarks set off prominent Clinton supporters, who said they smacked of sexism, notwithstanding the fact that Clinton made similar remarks about Barack Obama in 2008.

Sanders, who prides himself on never having run a negative political ad, backed down, describing his staffer’s remarks as “inappropriate.” But after a summer of setbacks, Clinton has taken a commanding position in the Democratic primary race. As the first primaries draw closer, the pressure will only grow to cut into Clinton’s lead by turning Democratic voters against her. And the Sanders campaign will be challenged to do so while maintaining the high-minded idealism and above-the-fray approach to politics that rallied grassroots enthusiasm behind him in the first place. 

Political veterans who support Sanders believe he’ll stand by his opposition to personal attacks. But some stress that his campaign needs to do more to prevent Clinton from taking advantage of anything that might be construed as out of line. “Bernie’s campaign and the leadership has to understand that you’re up against people who are masters of spinning," said Rep. Raul Grijalva, co-chair of the House Progressive Caucus, one of only two members of Congress who’ve endorsed Sanders. "Whatever is inadvertent, joking, tongue-in-cheek is not going to be taken that way."

At the same time, Grijalva believes that Sanders needs to be aggressive about going after Clinton. “If you’re hit, you hit back,” the Arizona Democrat said. “He can’t sit there and be a pin cushion.” I mentioned that the campaign has recently conducted polling to look at Clinton’s weaknesses, including her ties to big corporations and Wall Street, according to the New York Times. Would Clinton’s personal wealth be a fair target for Sanders? “I think that’s fair game,” he said, pointing out that Clinton’s campaign invariably has its own opposition-research file on Sanders. “I’m sure it’s locked and loaded and ready to use."

As Clinton has shown her strength—most recently at the first Democratic debate and the marathon Benghazi hearing—Sanders has gone after her more aggressively on policy, criticizing her latest comments on the death penalty (she opposes its abolition) and her past support for the Defense of Marriage Act. “There’s a difference between a candidate going negative and a candidate differentiating themselves from the others,” said House Progressive Caucus Co-Chair Keith Ellison, the other member of Congress who has endorsed Sanders. “I am proud of the Democratic candidates talking about who will do more to help working families, who will do more to protect the environment. That’s what we want.”

Sanders's grassroots supporters also say they welcome a head-on fight with Clinton on the issues. “It’s important for candidates to explain what they believe in. It’s important to draw distinctions. They are talking about the political arguments that are legitimate—not, ‘Because of this position, my opponent is unfit,’” said Charles Lechner, co-founder of People for Bernie, an outside group of grassroots supporters. 

But like the candidate himself, some of his biggest fans also have a strong aversion to thinking about the race in terms of the need to take down Clinton, stressing that the bigger principles that Sanders stands for are ultimately more important. “I’m not out to cut out Hillary’s support, I’m here to build up support for Bernie’s point of view, whether or not he wins the election,” said Laurie Dodd, who volunteers for the group Northern Virginia for Bernie Sanders.

I pointed to two post-debate polls last week that both showed Sanders trailing Clinton by about 40 points in Iowa, where he had previously trailed by the low single-digits. Even if those polls prove to be outliers, Clinton still has a 26-point lead nationally. “I don’t see the race as just a horserace. When we get together, we don’t talk about how close we are,” said Dodd. “The campaign is a success even if he’s not the eventual nominee, because it’s more than just Bernie Sanders the individual candidate.”

Robert Peters, a field organizer for the People’s Lobby of Illinois, a political action group that’s backing Sanders, voiced a similar sentiment. “Yes, we want Bernie to win, but what we want more than anything is to change the narrative in this country and change the narrative around the world,” said Peters. “Our work is more than just Bernie versus Hillary—it’s about how we can redefine the world as it is.”

The group has been canvassing across Chicago to build support for Sanders and Kim Foxx, a local candidate for Cook County state’s attorney. But it doesn’t lead off those efforts with conversations about Sanders. “Instead of talking about what the candidate can do, we knock on the door, and ask, ‘How is your life going?’” said Peters. “Then we talk to them about how Bernie is a champion of those issues.”

To a large extent, this echoes the core message of Sanders’s campaign: that it’s not about him as an individual, but a broader “political revolution” that aims to change the fundamental nature of American politics. For many progressives, that means creating a movement that can live beyond his campaign. But the strength of that movement will also depend, in part, on how well Sanders performs in the primary states and if he is able to rattle the political establishment.

Sanders himself has said that he would only ever “run to win” in 2016. And that, his top campaign staff believes, means confronting Clinton head on.