Four Democratic presidential contenders have accepted campaign contributions from lobbyists who represent foreign interests, according to a new report by the San Jose Mercury News.

Gov. Steve Bullock of Montana, former Colorado governor John Hickenlooper, former representative John Delaney of Maryland, and Gov. Jay Inslee of Washington have all accepted the contributions.

On the other hand, other Democratic candidates have vowed to reject such money and have thus far held firm to their pledges, including former vice president Joe Biden, Sens. Elizabeth Warren (D., Mass.), Bernie Sanders (I., Vt.), Kamala Harris (D., Calif.), and South Bend, Ind., mayor Pete Buttegieg.

The donations are allowable by law given that the persons in question are U.S. citizens; they happen also to lobby on behalf of a foreign government or entity.

"But at a time when many Democrats are increasingly worried about foreign influence in the U.S. political system—an issue put under the spotlight by Special Counsel Robert Mueller's congressional testimony Wednesday—rejecting the donations is a way for the candidates to shore up their good government bona fides," the Mercury News reported.

The set of candidates who have accepted contributions from foreign lobbyists compared to candidates who reject those donations appear to sort into two tiers.

Candidates doing well in fundraising such as Warren, Harris, and Sanders can afford to have a self-imposed ban on cash from foreign lobbyists, while the candidates that have accepted the contributions are struggling.

"Governor Bullock has been a leader in the fight against dark money and he will continue working to rid our system of its corrupting influence—and no contribution will ever impact that work," Bullock spokeswoman Galia Slayen said in an email to the Mercury News.

Hickenlooper and Delaney did not respond to the paper's request for comment, and Inslee told a reporter that he could not remember his campaign's policy on the matter. An Inslee spokesperson later said their campaign "was not screening its donations to reject lobbyist cash."

"Whatever we're doing is right," he joked, as reported by the Mercury News.