The organizers of the Women’s Convention — an outgrowth of the Women’s March that drew millions of participants around the globe in January — sparked controversy in mid-October when they announced that Sen. Bernie Sanders (I-VT) would be the conference’s opening-night speaker.

“This event is literally called the ‘Women’s Convention,’” Lily Herman wrote at Refinery29, “so it’d be nice to see, you know, women in the spotlight.” MSNBC host Joy-Ann Reid and many others expressed similar sentiments, as Vox’s Jeff Stein noted.

The organizers of the convention countered that their program included 60 women and only two men, and that they had invited a number of women — including Hillary Clinton, Sen. Kamala Harris (D-CA), and Sen. Elizabeth Warren (D-MA) — who were unable to attend. And while Sanders was slated to speak on opening night, Rep. Maxine Waters (D-CA) would give the keynote address.

In a statement on Thursday, Sanders announced that he would not attend the convention after all, and would instead travel to Puerto Rico to meet with Mayor Carmen Yulín Cruz of San Juan. But the controversy over Sanders has exposed larger rifts on the left, rifts that have to do with the 2016 primary but also with abortion rights, identity, and the interplay between feminism and economic policy.

Sanders’s comments about abortion are a sticking point for some feminists

As anyone who follows left-wing politics knows, conflicts between Sanders supporters and Clinton supporters have persisted long after the 2016 Democratic primary. Divisions in Democratic politics today are more complicated than Sanders versus Clinton, but as Stein notes, relitigation of the primary continues. That campaign included online harassment on both sides, and for many Clinton supporters, the memory of being attacked by Sanders supporters on Twitter doesn’t disappear overnight.

That’s part of the story behind the opposition to Sanders’s appearance. But it’s not the only part. Reproductive rights advocates have also been disturbed by Sanders’s post-election comments on abortion rights, as Rebecca Nelson notes at Cosmopolitan. Sanders endorsed Heath Mello, a mayoral candidate this year in Omaha, who had sponsored or voted for several anti-abortion bills during his time in the Nebraska state legislature. When criticized, Sanders said such choices might be necessary “if we’re going to become a 50-state party.”

“If you have a rally in which you have the labor movement and the environmentalists and Native Americans and the African-American community and the Latino community coming together, saying, we want this guy to become our next mayor, should I reject going there to Omaha?” he asked on Face the Nation.

“We have got to appreciate where people come from, and do our best to fight for the pro-choice agenda,” he told NPR. “But I think you just can't exclude people who disagree with us on one issue."

Sanders also noted that he has always voted in favor of abortion rights in Congress. But many saw his comments about the party as a betrayal of women, as well as of progressive values. “To be anti-choice on a policy level is absolutely indefensible from an economic justice, racial justice, gender justice and human rights standpoint,” Lindy West wrote at the New York Times. “And if the Democratic Party does not stand for any of those things, then what on earth is it?”

To others, Sanders’s willingness to budge on the issue of abortion was at odds with his campaign message of proud, unapologetic democratic socialism. If the left doesn’t need to compromise on a $15 minimum wage or single-payer health care, some wondered, why give ground on abortion rights? Herman wrote that the accusation that the Democratic Party wasn’t pragmatic enough was “rich coming from Sanders.”

Sanders has also come under fire for comments about women candidates

Sanders’s stance on anti-abortion candidates isn’t the only reason some feminists have concerns about the senator. Since the presidential election, he’s pressed the Democratic Party to “go beyond identity politics.” “Identity politics” means different things to different people, and as Graham Vyse of the New Republic points out, it’s not always entirely clear what Sanders means by it. But some of his comments about women candidates have troubled a lot of voters.

At an appearance in Boston in late November, Sanders got a written question from a woman named Rebecca: “I want to be the second Latina senator in U.S. history. Any tips?” Bringing more women of color into politics was important, Sanders said. But, he went on, “it is not good enough for somebody to say, ‘Hey, I’m a Latina. Vote for me.’ That is not good enough. I have to know whether that Latina is going to stand up with the working class of this country and is going to take on big-money interests.”

“It is not good enough for somebody to say, ‘I’m a woman. Vote for me,’” he added later. “What we need is a woman who has the guts to stand up to Wall Street, to the insurance companies, to the drug companies, to the fossil fuel industry.”

As Jeff Stein noted at the time, it was hard not to see this last comment as a criticism of Clinton. She and many of her supporters, however, would argue that her campaign was about more than her gender. And when it comes to Rebecca, it’s not clear why Sanders would assume her entire political message would boil down to “Hey, I’m a Latina. Vote for me.” The moment made him look like he was talking down to a woman eager to enter politics, even if that wasn’t his intent.

It also fed the fear among many feminists and other activists that Sanders might be willing to sacrifice racial and gender equality in favor of economic populism. “Economic policy is not the singular answer to violence, hatred, oppression, and marginalization,” Carmen Rios wrote at Argot in response to Sanders’s November speech. “That doesn't mean it isn't important — it just means we don't have to choose. It means we cannot choose.”

The Women’s Convention speech was an important test for Sanders

As the organizers of the Women’s Convention have noted, Sanders was just one of many speakers scheduled to appear at the event, and perhaps not the most prominent. Tamika Mallory, one of the organizers of the Women’s March, took media outlets to task on Twitter for devoting more attention to the Sanders announcement than to the news that Waters would deliver the keynote.

Maybe folks should ask why mainstream media didn't give a black woman the same attention when she was announced as a headliner & speaker? — Tamika D. Mallory (@TamikaDMallory) October 12, 2017

And ultimately, Sanders’s speech at the convention would probably have said more about him than about the convention itself. As a movement, the Women’s March has weathered controversies before and emerged strong enough to draw millions of people around the world and enrage the president. Whatever happens at the convention, it will be about much more than one man, no matter who he is.

Sanders, however, faced an opportunity — and a challenge. Many on the left, from his critics to his cautious supporters, have been wondering if there is room for feminism in his worldview. As Vyse wrote at the New Republic, “he’s never fully explained how he sees his populism pairing with identity politics. He needs to clarify that he is in fact talking about all Americans, and make it clear that he understands the distinct challenges faced by various groups.”

Sanders’s convention speech would have been a chance for him to do that, in front of a group that’s emerged, in the past 10 months, as a major political force. His choice to visit Puerto Rico instead was, in many ways, a smart one, allowing him to use his considerable star power to draw attention to a humanitarian crisis that President Trump has badly mishandled. But the challenge — whether he can speak convincingly on issues of gender and racial justice that he’s sometimes preferred to sidestep — remains.