At a moment when Bernie Sanders needs to show that he has broad appeal, the Vermont senator and White House hopeful is sticking to his comfort zone.

Sanders delivered an impassioned speech attacking Wall Street in Manhattan on Tuesday. The address was a virtual call and response of boos, jeers, and spirited applause in response to blistering criticism of corporate power and promises to reform a broken financial system.

Sanders pledged to break up big banks. (“If a bank is too big to fail, it is too big to exist!”) He vowed to check the power of the financial services industry by implementing “a 21st- century Glass-Steagall Act,” legislation beloved by progressive icon Elizabeth Warren that would separate commercial from investment banking. He painted Wall Street as a destructive force, capable of ripping apart “the fabric of our nation.”

The speech is sure to fire up Sanders loyalists. Anger over income inequality and the excess of Wall Street has been the animating theme of the senator’s presidential campaign. The address also gave Sanders an opportunity to draw a contrast with Democratic frontrunner Hillary Clinton, who has faced accusations of a cozy relationship with Wall Street.

Yet as the clock ticks down to the start of primary voting season, a focus on Wall Street may not be the best way to win converts, especially as Americans fret over national security and the threat of terror.  

Terrorist attacks in Paris and San Bernardino have heightened the significance of national security in the minds of voters. Sanders talks about security and the threat of terror on the campaign trail. He seemed to hit his stride during December’s Democratic debate, where he painted Clinton as a dangerous interventionist.

Security, however, remains a strong suit for Clinton. The former secretary of state appears at ease and knowledgable when the subject arises. Sanders, on the other hand, has struggled to shake off criticism that he seems far more eager to talk about income inequality than foreign policy. Viewed through that lens, Sanders’s Wall Street speech seems like something of a missed opportunity to broaden his appeal beyond a core economic message.

The Sanders campaign faces a challenge in the weeks ahead as it works to translate grassroots enthusiasm into voter turnout. Further complicating matters, polling suggests that Sanders may have hit a wall as he attempts to amass support.

To be sure, railing against big banks has the potential to strike a chord with voters on the left and the right. Populist anger in the aftermath of the financial crisis fueled Occupy Wall Street and the Tea Party. Sanders has already attracted support from Republican voters. The senator also hopes to win over Donald Trump fans by tapping into working-class anger. At this point, however, loudly repeating a well-worn message seems unlikely to sway any voter who hasn’t already sided with Sanders.

During his speech on Tuesday, the senator appeared to be preaching to the choir. The event was punctuated by cries of “We love you Bernie!” At one point, the audience finished Sanders’s sentence for him. “The reality is that Congress does not regulate Wall Street,” Sanders began. He stopped as the crowd took over, a chorus of voices enthusiastically yelling: “Wall Street regulates Congress!” “You got it,” Sanders said with a smile after pausing for applause to die down.  

A strategy focused on winning over conservatives with a fiery populist refrain faces structural hurdles. It’s one thing for a lifelong Republican to decide they like Sanders. It’s another matter for Republicans to vote for the senator in the primary, especially if that requires registering as a Democrat. While some voters have shown they are willing to do that, the extra step that would need to be taken in some states has the potential to complicate any plan by the campaign to court Republicans.

Still, Sanders’s Wall Street speech was a powerful reminder of the strength of his populist appeal. The senator has exceeded expectations in both the size of the crowds he manages to draw at campaign rallies, and the amount of small-dollar donations he pulls in. In December, the campaign announced it broke a record for the number of individual contributions taken in by a presidential campaign at this point in the race.

That grassroots appeal shone clearly in Manhattan as Sanders raised the specter of the financial crisis, and promised a new, and better, way forward. Standing in front of an energized crowd, Sanders declared: “Here is a New Years’ Resolution that I will keep, if elected president, and that is: If Wall Street does not end its greed, we will end it for them!” The crowd erupted into cheers of “Bernie! Bernie! Bernie! Bernie!”

What remains unclear is whether the strength of that appeal will be enough.