Sen. Bernie Sanders’ (I-VT) campaign is reportedly unhappy with the stump speech Rep. Alexandria Ocasio-Cortez (D-NY) delivered in Sanders’ absence on the campaign trail during the Senate impeachment trial and fears her strong rhetoric could alienate voters in Trump-won battleground states like Wisconsin, Pennsylvania, and Michigan, according to a report from Vanity Fair.

Ocasio-Cortez went on the campaign trail for her candidate in Iowa during the Senate impeachment trial, which kept Sanders locked down in the nation’s capital, compromising his ability to campaign in the Hawkeye State ahead of its caucuses. According to Vanity Fair, Ocasio-Cortez’s performance “stoked some tensions between herself and the Sanders campaign” and caused some to fear that her “off script” performance could jeopardize Sanders’ chances of resonating with voters in Wisconsin, Pennsylvania, and Michigan — three states President Trump narrowly won in 2016.

Sanders’s campaign manager, Faiz Shakir, reportedly sent a message to the New York lawmaker’s campaign manager critiquing Ocasio-Cortez’s performance, “according to a source familiar with the exchange.” Shakir was reportedly bothered that Ocasio-Cortez did not mention Sanders’ name during the rally at the University of Iowa last month. Her rhetoric on breaking apart U.S. Immigration and Customs Enforcement (ICE) and Customs and Border Protection (CBP) and “tipping people off” on their presence in order to “keep people safe” also raised eyebrows.

“Organizing is about tipping people off if you start to see that ICE and CBP are in communities to try and keep people safe,” she said during a Sanders campaign event in Ames, Iowa, adding that Sanders is “actually committed to breaking up ICE and CBP”:

Ocasio-Cortez’s comments about the abolition of U.S. Immigration and Customs Enforcement and Customs and Border Patrol were also seen by some within the Sanders campaign as going too far, straying from Sanders’s stance on the issues in encouraging people not to cooperate with law enforcement agencies, according to this source.

The magazine described immigration as a “hot button” issue in several Trump-won battleground states, particularly in the Rust Belt. Her message reportedly concerned some who “felt that AOC had gone off script” and now fear that she could alienate voters in those key states with her direct, absolutist rhetoric on those issues.

While Ocasio-Cortez’s campaign declined to comment on the matter, Vanity Fair reported that the Sanders campaign, officially, said the Sanders surrogate “was not off message and how she talks about these issues is how Senator Sanders talks about these issues.

According to the magazine, Ocasio-Cortez and her team were “said to be annoyed” by the critiques and concerned over podcast host Joe Rogan’s seeming endorsement for Sanders, although the Sanders campaign told Vanity Fair that “no such concerns about Rogan were raised.”

Despite the rumors of internal tension, Ocasio-Cortez has continued to stump for her candidate, speaking at the socialist senator’s massive rally at the Whittemore Center Arena in Durham, New Hampshire, ahead of state’s primary. The rally, which drew 7,500 attendees, featured the actress Cynthia Nixon, activist Cornel West, and the rock band The Strokes.

“We have to nominate somebody with a political revolution at their back,” Ocasio-Cortez told the crowd.