Sen. Ed Markey (D-Mass.), a Green New Deal co-sponsor, last week returned $46,900 in donations after violating a pledge to reject money from the fossil fuel industry by accepting contributions from lobbyists who worked for oil and gas companies.

In the first six months of this year, the senator raised $10,000 from six lobbyists whose clients included oil giants Chevron and BP. His campaign received an additional $5,000 from four lobbyists who worked for fossil fuel companies, according to a third-quarter Federal Election Commission filing released last week.

The campaign contributions, activists said, violated the No Fossil Fuel Money pledge, a popular oath overseen by more than a dozen environmental groups, which Markey signed in December. Signatories to the pledge vow to turn down donations of over $200 from oil, gas, and coal industry executives, lobbyists, and PACs.

But a thorough review found 28 donations that violated the pledge, namely frolobbyists whose clients included, but were not primarily, fossil fuel firms. The loophole exposed a gap in a pledge thats become a key litmus test for how seriously Democrats take the corrupting influence of an industry increasingly accused of crimes against humanity .

MassLive first reported the campaigns decision.

The activists who supervised the pledge last Wednesday sent an updated set of guidelines to the more than 1,800 campaigns who have signed, including a database of politically active fossil fuel companies to avoid.

Following this clarification, the campaign identified donors who met a technical requirement of the No Fossil Fuel Money Pledge, of which we were previously unaware, John Walsh, Markeys senior campaign director, said in a statement. We quickly worked to ensure technical compliance with the pledge.

Oil Change U.S., one of the main groups that control the pledge, offered forgiveness.

Campaign finance is a sticky wicket, so we understand that mistakes will be made, Collin Rees, a senior campaigner with the nonprofit, said in an email. Taking ownership of those mistakes and rectifying them quickly is precisely in the spirit of the pledge, and exactly what we need to see from politicians willing to stand up to the fossil fuel industry.