Sen. Elizabeth Warren (D-MA) has had a relatively lax campaign as far as opposition goes, with ideological ally Sen. Bernie Sanders (I-VT) refusing to criticize her. However, other campaigns are ramping up their opposition research and planning to take Warren on in the next debate, according to campaign aides who spoke to Politico.

Sanders – who has been Warren’s closest ally in the race – has repeatedly refused to take the Massachusetts senator on, arguing that it “is not the way you necessarily win a campaign.” However, with Warren solidifying herself as a top tier candidate with growing momentum, other campaigns are ramping up their efforts and preparing to challenge her in the next debate.

Politico reports:

Aides to three rival candidates confirmed in interviews they’re revving up opposition research on Warren in preparation for the next debate on Sept. 12. Still others privately complained she’s gotten fawning treatment in the media as she unveiled a litany of ambitious plans without being pressed on where the money would come from to pay for them. Warren’s supporters said the gripes amount to sour grapes from campaigns who didn’t take her seriously until she shot up in the polls, and are now watching with envy the organization she’s amassed while they were busy attacking each other.

Her competitors do not want to alienate potential voters in the process. Campaign aides, though, have signaled that their candidates will be ready to attack if Warren chooses to go on offense:

An adviser to a competing campaign, who spoke on condition of anonymity, echoed some of that sentiment. If Warren attacks someone else’s record on the debate stage, the person said, she will get it back in return. “Nobody else here has been a Republican before,” the adviser said.

As Breitbart News previously reported, Warren has been using Sanders as somewhat of a human shield, agreeing with his aggressive proposals – like Medicare for All and a Green New Deal plan – but allowing him to take the brunt of the questions and criticisms.

As Breitbart News reported:

While it is true that most criticisms of Medicare for All have been geared toward Sanders, he has been demonstratively more vocal and honest about his efforts. Warren, however, has yet to provide details of her comprehensive plan, which may explain why she has not had as much of a target on her back.

Nonetheless, some campaigns believe that Warren’s momentum will slow, much like Sen. Kamala Harris’s.

“It’s inevitable: What goes up must come down. It’s the law of political physics,” Joe Biden (D) organizer Dick Harpootlian said, according to Politico.

Warren is currently averaging 16.5 percent in the polls and will face nine candidates – including Biden, Harris, and Sanders – on the debate stage in Houston, Texas, September 12.