Marissa Johnson, left, speaks as Mara Jacqueline Willaford stands with her and Democratic presidential candidate Sen. Bernie Sanders, I-Vt., stands nearby as the two women take over the microphone at an Aug. 8, 2015 rally in Seattle.  (AP Photo/Elaine Thompson)

For all of Bernie Sanders’s success this campaign so far, there’s been one issue on which he still can’t seem to please his critics: Race relations.

Specifically, Sanders has struggled in his ability to talk — in detail — about what he’d do in response to the prevailing sense in America that race relations are getting worse, not better. For Sanders, the answer has often been simple. It lies in his core philosophy that if you tip the scales of income inequality away from billionaires and back toward the people, things will get better.

And that response, for better or worse, hasn’t really changed — even as the media continues to question whether Sanders can right the ship when it comes to appealing to minority voters. Black voters, in particular, favor Hillary Clinton overwhelmingly. And that becomes much more important as more diverse states prepare to vote on who the Democratic nominee should be.

When asked at Thursday’s Democratic debate in Milwaukee whether he sees the economic struggles of Americans in terms of race, Sanders said something instructive.

“We can talk about it as a racial issue, but it’s a general economic issue,” he said.

That is not what the Black Lives Matter protesters — who halted not one, but two of his campaign events this summer to try to get him (and all presidential candidates) to recognize racial injustice as a separate, pressing issue — want to hear.

When Black Lives Matter protesters stopped Sanders’s speech in July at Netroots Nation, Sanders got frustrated they weren’t letting him speak and threatened to walk offstage.

In Seattle a month later, Black Lives Matter protesters shut down one of his rallies once again.

Sanders was yet again defiant. He hired a Black Lives Matter supporter to be his press secretary. (She said she advised him that "racial inequality and income inequality are parallel issues.") He pointed out his record fighting for civil rights in the 1960s; he was arrested for protesting segregation in public schools in Chicago.

And then he went right back to his overarching message of income inequality.

“I think it is unfortunate because, among other things, I wanted to talk about the issues of black lives, the fact that the American people are tired of seeing unarmed African-Americans shot and killed,” Sanders told CNN after the Seattle protest. “But there are other issues, as well, that we have to talk about, and that is the fact that the middle class of this country is disappearing.”

Several months later, Sanders has beaten or nearly beaten Clinton in two states that happen to be among the whitest in the nation. He’s made clear he thinks policing reform and criminal justice are critical issues that need to be addressed. And yet, in Democrats’ debate Thursday, “Wall Street” made it into the first sentence of Sanders’s answer about what he’d do for race relations that President Obama hasn’t.

“Yes,” he said unequivocally when asked for a second time whether he really thinks race relations would improve under him.

The reason why he’s so confident, you probably won’t be surprised to hear, lies in taxing billionaires “to create millions of jobs for low-income kids so that they’re not hanging out on street corners.”

The problem with being so singularly focused on one solution to many problems is that, to many supporters who might sympathize with the aims of Black Lives Matter, it feels like Sanders hasn’t fully understood the magnitude of their problem. Sanders’s “they-will-eventually-get-it” argument, as The Fix’s Janell Ross wrote, can even come across as patronizing.

Whether they agreed or disagreed, Hillary Clinton and Bernie Sanders had to work hard to differentiate themselves at Thursday's debate. (Peter Stevenson/The Washington Post)

And that’s especially the case when the candidate standing next to him on the debate stage is Clinton, who on Thursday used such race-related questions to tick off all sorts of specifics as to how she’d progress race relations after Obama. She’d focus on policing reforms, yes, but also invest in housing, education and jobs.

“I particularly appreciate the proposal that Congressman Jim Clyburn has — the 10-20-30 proposal — to try to spend more federal dollars in communities with persistent generational poverty,” she said at one point. (Clyburn is, of course, the Democrats’ third-in-command and an African American from South Carolina.)

Notably, when she was done talking, Sanders shared his “race-is-an-economic-issue” line.

Nobody, of course, has all the answers. In Thursday’s debate, Clinton said she’d “build on an honest conversation about what comes next.”

But Sanders doesn’t want to seem to have that conversation — and he doesn’t seem to have adjusted course when it comes to broadening his approach to wooing minority voters.

Refusing to do either of those things may come at his own political peril.