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.