Some Democrats are putting up caution signs for Hillary Clinton as she wades back into presidential politics by casting 2020 candidate Tulsi Gabbard as a “Russian asset,” mocking President Donald Trump’s dealings with a foreign leader and drawing counterattacks from both.

Bernie Sanders, who lost the 2016 nomination to Clinton and is running again in 2020, took to Twitter with implicit criticisms of his erstwhile rival. “People can disagree on issues,” Sanders wrote Monday, “but it is outrageous for anyone to suggest that Tulsi is a foreign asset.”

Larry Cohen, one of Sanders’ top supporters, was more conciliatory but warned in an interview that Clinton could harm the eventual 2020 nominee by weighing in against specific candidates, even a longshot like Gabbard.

The former first lady, U.S. senator and secretary of state has “put a lifetime into the Democratic Party. She deserves to be heard,” said Cohen, a prominent member of the Democratic National Committee who also chairs Our Revolution, the spinoff of Sanders’ last presidential campaign. But “in this senior leader role she has,” Cohen said, “it’s her job to embrace the range of politics within the party and not polarize within it.”

Her scuffle with Gabbard and other recent headlines she’s driven demonstrate the 71-year-old remains a political lightning rod, just as she’s been through much of the last three decades. The dynamics raise questions about how Clinton and her party can best leverage her strengths and navigate her weaknesses through next November.

For her part, aides say Clinton isn’t attempting any calculated play.

“The short of it is that she’s on a book tour and is feeling unconstrained about speaking her mind,” said Clinton spokesman Nick Merrill. “It’s easy to over-ascribe a strategy about every word she utters, but it’s as simple as that. She’s out there telling the truth.”

Yet the results can frustrate those trying to win the office that Clinton twice lost, a reality presidential hopeful Cory Booker observed with a carefully calibrated critique while he campaigned Monday in New Hampshire. “We need to focus on winning this election … talking about the urgencies that we have before us and not indulging in what I think is, for me, not a relevant story,” Booker said, targeting the news media more than Clinton or Gabbard.