The group’s field operation started at the beginning of February and includes 13 paid canvassers. The team said it has knocked on more than 3,000 doors and made more than 27,000 phone calls and sent more than 24,500 texts. It has also visited churches and held town halls.

Potter’s group has not endorsed a Democratic presidential candidate and does not promote anyone in its messaging. However, he acknowledged that its spending could benefit Sanders and Warren, who support single-payer health care.

“It’s a potential side effect,” he said. “But that’s not our intent.”

Sanders is particularly poised to gain from the campaign, since he is the overall primary frontrunner and the contender most associated with Medicare for All.

Joe Biden, who opposes single payer, is in the lead in the South Carolina primary, according to polling averages, with Sanders in second place.

The Partnership for America’s Healthcare Future, an alliance of pharmaceutical, hospital and health insurance lobbyists, bought $200,000 in anti-Medicare for All TV ads this week to air in South Carolina. The industry group has spent a total of more than $2 million on spots in Iowa, Virginia and North Carolina, according to Advertising Analytics.

Pete Buttigieg also criticizes Sanders over his single-payer plan in an advertisement on TV in the state.

Medicare for All Now’s online spots feature Shaun King, a Sanders surrogate, and Ady Barkan, a dying activist and prominent Warren backer. “While executives and companies are making billions of dollars in profit, they’re doing it at the expense of our health,” one states. Another ad ties South Carolina’s high eviction rates to exorbitant medical costs.

In the presidential primary's first three contests, polls show that 6 out of 10 voters backed Medicare for All.