Elizabeth Warren finds herself in a delicate position. Right as her popularity in the Democratic presidential contest is rising, the race has taken a dramatic turn: Her main rival for the nomination is under attack by the president.

She has been left with a choice: forcefully defend former Vice President Joe Biden against President Donald Trump’s debunked accusations of misconduct in Ukraine by his son Hunter, or risk looking like she’s taking advantage of Trump’s attack on her top opponent to boost her own presidential campaign.

Warren, so far, has kept her attention primarily on the need for impeaching the president, which she has championed for five months and which House Democrats are now embracing in droves. And Democratic operatives caution that she should continue spending her time focusing on the Trump and not her primary rival.

“This isn’t about Joe Biden. This is about Donald Trump,” Rebecca Katz, a progressive Democratic strategist told The Daily Beast when asked how Warren’s campaign should address the issue. “On the defining issue of the Trump era, Warren has been right since day one.”

“Look, she should pat herself on the back and remind everybody she called for impeachment before everyone else,” Democratic strategist Mary Anne Marsh, who has long praised Warren’s presidential candidacy, said. “Joe Biden honestly has nothing to do with this.”

Warren’s handling of the Trump-Ukraine saga illustrates the tricky politics that many Democrats currently find themselves in, including Biden’s own campaign. Few Democrats are eager to elevate Trump’s attacks on the former vice president by engaging them head on. But virtually no one in the party feels comfortable letting them go unanswered. The question is how to do so.

In interviews with multiple progressive Democrats and Warren supporters, their chief advice to Warren is don’t rush to Biden’s defense against Trump, but don’t jab him over being slower to call for impeachment inquires, either.

“There will be plenty of time for real policy differences with Joe Biden, but the biggest Trump corruption scandal of his presidency is not the time to do it,” said Adam Green, cofounder of the Progressive Change Campaign Committee, a Washington-based organization that has endorsed Warren’s presidential bid. “We need 100 percent all hands on deck calling for impeachment right now.”

The comments come as more than 160 House Democrats are now calling for some degree of impeachment inquiry.

“I called for impeachment five months ago, the day after the Mueller Report came out,” Warren wrote on Twitter on Tuesday, without addressing Biden. “Trump continues to commit crimes because he believes he’s above the law. If Congress does nothing to respond, he’ll be right,” she continued. “We must begin impeachment proceedings—now.”

Biden has been noticeably slower than his Democratic opponents on the issue that has reached a new height this week. On Tuesday afternoon, he took a stronger stance than in the past when addressing how House Speaker Nancy Pelosi should move forward.

“Using its full constitutional authority, Congress, in my view, should demand the information it has a legal right to receive,” Biden said from Delaware. If the president refuses to cooperate, Biden added, “Trump will leave Congress, in my view, with no choice but impeachment. That would be a tragedy, but a tragedy of his own making.”

Biden’s new stance—and Warren’s doubling down—comes as a pair of early state polls released in recent days from Iowa and New Hampshire show Warren narrowly beat out Biden for the number one spot in the respective states.

“Voters respond to moral clarity and courage, and Senator Warren showed it in spades with her early call for impeaching Donald Trump,” Maurice Mitchell, the national director of the Working Families Party, which recently endorsed Warren, told The Daily Beast.

“It's great to see others in the field follow her lead,” he said, without referencing Biden.

Warren's campaign declined to comment.

One Democratic communications operative supportive of Warren stressed that the best course of action is to focus on her own campaign and not address Biden by name.

“She’s not facing pressure from voters on this, so she should continue her focus on how she’ll root out corruption to make real change in people’s lives,” the operative said. “If she’s going to weigh in, she should condemn the media’s willingness to blur the lines.”

In late April, Warren was the first major Democratic presidential candidate to call on the House to begin impeachment proceedings against Trump. Her call came immediately after the release of Special Counsel Robert Mueller’s report on Trump and Russia.

“The severity of this misconduct demands that elected officials in both parties set aside political considerations and do their constitutional duty,” she wrote on Twitter at the time. “That means the House should initiate impeachment proceedings against the President of the United States.”

Since then, Warren has grown increasingly fervent in pushing the issue.

In her most recent public showing during a Democratic cattle call in Iowa, Warren started off her speech amplifying her previous sentiments, while saying she’s there “to stand up for the Constitution” and that “Congress failed to act” in impeaching Trump, impressing voters in the influential caucus state.

“She read the report. She didn’t do any poll testing about how this is going to look. She looked at the facts and decided to do what’s right. Voters are hungry for a leader who has the courage of their convictions,” Katz said.

So far, there’s been considerable upside for Warren. Multiple polls showed her popularity increasing after she called for impeachment in the spring. And the number of small-dollar donations grew. Additionally, Warren’s campaign brought in more than $19.1 million in the second quarter of the year, more than tripling her total for the first quarter.

“You keep it about the facts,” Katz added. “This isn’t about whether or not to defend a rival. This is about the rule of law.”