(CNN) Pete Buttigieg's presidential campaign has reversed its decision to accept donations from registered lobbyists and says it will refund the contributions it has received so far.

Buttigieg's campaign manager, Mike Schmuhl, said in an email Friday that the campaign will send back $30,250 it had received from 39 individuals.

"Mayor Pete will not be influenced by special-interest money, and we understand that making this promise is an important part of that commitment," Schmuhl said in the email to supporters.

"Standing up for our collective values not only includes saying we believe that campaigns should not take money from lobbyists; it also means being aware of the loopholes that still allow special interests to impact the campaign," he said.

The decision by the mayor of South Bend, Indiana, reflects a reality of the 2020 Democratic presidential primary: The cost of being exposed to attacks from opponents who are turning lobbyist money away and activists could exceed the benefit of that money.

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