About a month ago, during the sixth debate for the Democratic presidential candidates, PBS’s Judy Woodruff asked Hillary Clinton and Bernie Sanders about U.S. race relations in the Obama era. Clinton responded by emphasizing some areas of improvement, while also describing “the dark side of the remaining systemic racism that we have to root out in our society.” Her efforts as president, she said, would focus on criminal justice reforms, education, jobs, and housing.

When the question about racial divisions went to Sanders, the Vermont senator immediately turned to “the disastrous and illegal behavior on Wall Street.” When the moderator asked if race relations would be better under a President Sanders, he responded, “Absolutely.” Why? Because if he’s elected, he’ll change tax policy to stop “giving tax breaks to billionaires.”

The exchange stood out for me because it was such a striking reminder about Sanders’ approach. He has a specific message, which he’s eager to connect to practically any issue. It’s easy to imagine Sanders going to lunch, getting asked what he’d like to order, and hearing him respond, “I’d like a turkey on rye, which reminds me of how the economy is rigged against working families.”

Last night, I believe for the first time, Sanders acknowledged that one of Clinton’s criticisms of his candidacy is probably correct.

“[L]et us be clear, one of the major issues Secretary Clinton says I’m a one-issue person, well, I guess so. My one issue is trying to rebuild a disappearing middle class. That’s my one issue.”

At another point in the debate, Sanders even connected the Flint water crisis to, of all things, Wall Street.

Keep in mind, it wasn’t long after Clinton raised concerns about Sanders being a “single-issue” candidate that he rejected the label out of hand. “I haven’t the vaguest idea what she’s talking about,” he said a couple of weeks ago, adding, “We’re talking about dozens of issues so I’m not quite sure where Secretary Clinton is coming from.”

But the answer in this latest debate was different, though it was probably more of a repackaging than a reversal. Sanders is still “talking about dozens of issues,” but as of last night, he’s effectively making the case that the issues that are most important to him – economic inequality, an unfair tax system, trade, Wall Street accountability, etc. – fall under the umbrella of a broader issue: rebuilding the middle class.

In other words, Sanders is willing to present himself as a single-issue candidate, so long as voters recognize the fact that his single issue is vast in scope.

This isn’t altogether expected. In recent weeks, Clinton’s principal criticism of Sanders is that his areas of interest are far too narrow. As of last night, Sanders has stopped denying the point and started presenting it as a positive.

And who knows, maybe it is. Democrats have been focused on the interests of the middle class for generations, and when Sanders made his “one-issue” declaration, the audience applauded.

But it’s not every day that a candidate announces during a debate that one of the central criticisms of his candidacy is broadly accurate.

During last night’s debate, Clinton let Sanders’ acknowledgement go without comment – she did not repeat the “single-issue candidate” criticism – but it creates an interesting dynamic in their race. Remember, as we discussed a month ago, Clinton wants voters to see Sanders as a well-intentioned protest candidate. The White House is about breadth and complexity, the argument goes, and even if you agree with Sanders, it’s hard to deny his principal focus on the one issue that drives and motivates him.

A president, Clinton wants Democratic voters to believe, doesn’t have the luxury of being “a one-issue person.” A president’s responsibilities are simply too broad to see every issue through narrowly focused lens.