U.S. Rep. Tulsi Gabbard has pledged to forgo campaign contributions from political action committees, commonly known as PACs, joining just a handful of other members of Congress who have recently rejected the money from special interest groups.

The congresswoman, who represents the neighbor islands and rural Oahu, faces re-election in 2018, though there has also been speculation for several years about whether she might seek higher office.

Gabbard has been included on national media lists of possible female contenders for the presidency in 2020, and a Facebook group called Run Tulsi Run has attracted more than 30,000 members. Gabbard told the Honolulu Star-Advertiser last month that she did not plan to run for president.

Gabbard said that her decision to reject PAC money stemmed from a pledge she made to herself when she was first elected to Congress to not allow money to influence her decisions. She says she’s also refused to accept money from Wall Street banks, large pharmaceutical companies, tobacco and liquor companies, and more recently the defense industry.

“Here’s the bottom line: We cannot allow the future of our nation and our politics to be driven and shaped by special interests,” Gabbard said in a statement last week announcing her decision.

PACs are often set up by powerful corporate interests, such as defense contractors and health insurance companies, but they can also represent the interests of unions or groups advocating on behalf of issues such as women’s rights, the environment or veterans affairs.

The committees can donate up to $5,000 to a candidate in both the primary and general elections. Top PACs often spend several million dollars in a single election cycle, spreading it out across dozens of candidates.

During the 2016 election cycle, 21 percent of Gabbard’s campaign contributions, or about $477,000, came from PACs, according to the Federal Election Commission. The congresswoman received money from PACs representing companies such as Alexander &Baldwin, Lockheed Martin and Boeing, and unions representing electrical workers, ironworkers and the aerospace industry.

“Members of Congress are under constant pressure to raise money for their next election,” said Corie Tanida, executive director of Common Cause Hawaii, which advocates for open and accountable government. “Too often, money is a barrier to mounting a competitive campaign, and PACs fill the fundraising gap. They can also play an outsize role in dictating the policy agenda in Washington.”

While rejecting PAC money can help stem the influence of special interests in politics, it doesn’t preclude it. Company officials can still donate individually to campaigns.

For instance, during the 2016 campaign, Gabbard received $7,400 in individual contributions from Alexander &Baldwin officials and $16,710 from Navatek employees.

Rejecting PAC money also doesn’t stop the influence of “super PACs,” which can raise and spend an unlimited amount of money to support or defeat candidates as long as they act independently and don’t coordinate their activities with a candidate or campaign. Super PACs have been particularly controversial because donors don’t have to be disclosed, leading to what critics say is a proliferation of “dark money” in politics.

It’s difficult to track how many other congressional candidates are joining Gabbard in rejecting PAC money this current election cycle, but at least six members of the House rejected such money during the 2016 election cycle, according to CleanSlateNow.org, which tracks contributions.