As Sen. Bernie Sanders sinks to a distant third in a number of new national and early voting state polls, top members of his presidential campaign are taking aim at Sen. Elizabeth Warren of Massachusetts -- the other progressive superstar in the Democratic nomination race who’s soared ahead of Sanders in the surveys.

The swipes signal what could be a newly aggressive phase for the Vermont senator's campaign, with a hitherto "truce" between him and Warren beginning to crack as his polling numbers suffer. One progressive strategist with ties to the independent senator’s campaign said that when it comes to negating Warren’s surge in the polls, the Sanders team has been “flailing around.”

WARREN SURGES IN LATEST POLLS, TIES BIDEN FOR TOP SPOT; SANDERS SLIPS TO DISTANT THIRD

Sanders and Warren met last December before they launched their presidential bids and agreed to not criticize each other while on the campaign trail. That non-aggression-style pact has largely held – with both teaming up at recent presidential debates to defend their "Medicare-for-all" proposals.

And both had refrained from attacking each other.

“Bernie and I have been friends for many, many years. Long before I ever got into politics. And I don’t see any reason that that should change,” Warren told reporters recently after being asked if she was going to start painting contrasts with Sanders.

Sanders – who’s making his second straight White House run – has repeatedly said when asked about Warren that “Elizabeth is a friend of mine” and noting that the two “have been friends for over 20 years.”

But that’s apparently not stopping some leading members of Sanders' team from taking aim at Warren.

The Sanders campaign’s national press secretary Briahna Joy Gray recently criticized Warren on Twitter for failing to support Sanders’ national rent control proposal. Warren has said she doesn’t think such a policy would be realistic across the country. Gray used Warren’s viral zinger from the July debate in targeting the senator from Massachusetts.

Gray also jabbed at Warren over her campaign's lack of a collective bargaining agreement with her staff since recognizing her campaign workers’ union in June.

Sanders also faced a bit of criticism as he met the demands from his own unionized campaign staff.

In another case, senior Sanders adviser Warren Gunnels took aim at Warren’s climate change plan. As Vox noted, Gunnels retweeted a tweet from a New York City councilman saying that Warren had “missed the mark.”

As they were battling for second place in the polls most of the summer, the Sanders campaign repeatedly insisted that former Vice President Joe Biden was the main target. The former vice president was the clear front-runner in nearly all polling from his entry into the race in late April until recent days, when a slew of new surveys suggested that Warren had tied Biden for the top spot.

WARREN LANDS BACKING OF PROGRESSIVE GROUP THAT ENDORSED SANDERS IN HIS 2016 PRESIDENTIAL BID

While Sanders kept his focus on Biden, Warren surged in polling and, in a well-publicized moment, she landed the endorsement of the progressive group the Working Families Party, which backed Sanders four years ago in his first White House bid. Meanwhile, Sanders in recent weeks has replaced a couple of key staffers in Iowa and New Hampshire, the states that kick off the presidential primary and caucus calendar.

“They thought their opponent was Biden because they thought he was the next Hillary Clinton,” noted the progressive strategist, who asked to remain anonymous to speak more freely.

The strategist argued that the Sanders campaign failed to realize that Warren was the real threat, spotlighting that “their strategy was wrong. They were looking at Biden as the main opponent when it was really Warren.”