Top Clinton campaign staffers worried about "blowback" from their own supporters if they attacked Bernie Sanders on the issue of gun control, a series of hacked emails released on Tuesday show.

In a March 2016 email chain involving some of the most prominent members of Hillary Clinton's presidential campaign, campaign chairman John Podesta and communications director Jennifer Palmieri expressed concern over a draft of a Hillary Clinton op-ed the campaign planned to place in the New York Daily News. Though the draft is not included in the email chain that was released to the public, the op-ed is described as being about "gun violence."

The emails were posted online by Wikileaks. The director of national intelligence and Department of Homeland Security have accused "Russia's senior-most officials" of hacking and leaking emails posted to Wikileaks and other sites to influence and interfere with the 2016 election.

Podesta expressed concern in the email chain over apparent attacks on Bernie Sanders’ record on guns. "Should we directly hit Sanders in this NYDN oped right now?" he asked. "I'm a bit skeptical."

Palmieri responded that she thought the attacks may be too strong as currently drafted, but argued some contrast was important. "Maybe it is too hard here – but thought we should have some measure of contrast," she wrote.

She also laid out a strategy for how the campaign should deal with Donald Trump—arguing they should avoid a one-on-one fight with him over gun control at that point. "My theory is that we do not want to be in a one on one with Trump – but want to hit him occasionally," she said. "In which case, we also need to be hitting Sanders occasionally so we can credibly say we are not only focused on the general."

Palmieri went on to say that the difference between Hillary Clinton and Bernie Sanders on gun control, an issue where Hillary ran to the left of Sanders, tested well. She added that the campaign had already planned to use the issue in an upcoming press call.

"For example, we were going to do a press call tomorrow in AZ with locals about guns (number one testing contrast issue)," she said. "So I thought good to do here."

Podesta wasn't convinced. "Interestingly, I am worried about blowback from our supporters," he said.

Podesta didn't expand on why he believed the campaign would face backlash from Clinton supporters if they hit Sanders too hard on guns. Palmieri backed down in her response—agreeing to an op-ed "with less contrast."

The Clinton campaign did not immediately respond to a request for comment.

The New York Daily News ended up publishing an op-ed under Hillary Clinton's byline titled "Take dead aim against gun violence: Hillary Clinton urges closing loopholes that cost lives" on March 27, 10 days after the email chain ended. The op-ed included a single paragraph on the differences between Clinton and Sanders.

"This highlights a genuine difference in the Democratic presidential primary," the op-ed said. "On each of these critical issues — legal protections for gun makers, background checks and the Charleston loophole — my opponent voted with the NRA. In one recent debate, he defended one of these votes, and the NRA even tweeted that Senator Sanders ‘was spot-on in his comments about guns.'"

"If the NRA thinks you're doing a good job, that's a pretty good indication that something's very wrong."

The op-ed also included a single reference to Donald Trump. "Donald Trump has called the NRA's efforts to stop gun safety reforms ‘invaluable,'" the piece said. "He has vowed to ‘un-sign’ all of President Obama's executive actions to strengthen background checks. And he has pledged that on his very first day in office he would override laws that prevent people from carrying guns into schools."