Senator Bernie Sanders attacked former South Bend, Indiana Mayor Pete Buttigieg for taking campaign donations from billionaires, leading to #PetesBillionaires trending on Twitter.

Buttigieg accepted donations from 40 billionaires or their spouses, while Bernie has accepted none, a Forbes analysis of campaign donations found.

Both California Senator Kamala Harris and former Vice President Joe Biden had more billionaire backers than Buttigieg, however.

Buttigieg found himself under fire in December for attending a fundraiser in a wine cave where guests paid $2,800 to dine under a chandelier covered in 1,500 Swarovski crystals.

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#PetesBillionaires is trending on Twitter after Senator Bernie Sanders attacked Pete Buttigieg for using donations from billionaires to fund his presidential campaign.

At a breakfast event in New Hampshire on Friday, Sanders read aloud a series of headlines calling Buttigieg a “big business candidate” that “has most exclusive billionaire donors of any Democrat,” The Washington Post reported.

The hashtag began trending Friday afternoon after Sanders tweeted screenshots of the headlines.

A representative of Buttigieg’s campaign told Business Insider that while the former mayor believes campaign finance reforms are needed, such changes can not be made if he does not have the necessary resources to defeat President Trump.

6% – percent of America’s billionaires that have *donated* to Pete Buttigieg’s campaign (40/621). 1% – percent of Latinos supporting Pete Buttigieg according to latest polls. 0% – percent of black people supporting Pete Buttigieg according to latest polls.#PetesBillionaires — Michael Sayman (@michaelsayman) February 7, 2020

THIS HAPPENED —> The New York Times reported that @PeteButtigieg personally attended a secret meeting of big donors as they formulated plans to try to destroy @BernieSanders. #PetesBillionaireshttps://t.co/c3QPjlAyzj — David Sirota (@davidsirota) February 7, 2020

Buttigieg received campaign donations from 40 billionaires and their spouses, including the wife of former Google CEO Eric Schmidt, Netflix CEO Reed Hastings, and hedge fund manager Bill Ackman, a Forbes analysis of campaign documents published in December found.

Sanders himself received a $470 donation from a billionaire spouse, but promptly returned it, Forbes reported.

Wealthy backers have become an increasingly big optics problem for Buttigieg. The 38-year-old miltary veteran found himself under fire in December after attending a fundraiser in a wine cave where guests paid $2,800 to dine under a chandelier covered in 1,500 Swarovski crystals.

Here are some photos of the Buttigieg fundraiser in Napa — with the famous wine cave and the chandelier with 1,500 Swarovski crystals — that @BrianSlodysko wrote about.https://t.co/0sprQ3aDsy pic.twitter.com/3waO6jO93L — Teddy Schleifer (@teddyschleifer) December 16, 2019

Both California Senator Kamala Harris and former Vice President Joe Biden have had more billionaire backers than Buttigieg, however. Biden accepted donations from 44 billionaires, Forbes reported. Harris had the financial support of 46 before dropping out of the race in December.

The majority of Buttigieg’s campaign funding comes from small donors, the Washington Post reported, including $2.7 million from 22,000 new donors after the Iowa Caucuses.

Sanders’ comments come four days after the two Democrats finished neck and neck in the Iowa Caucus. Both Sanders and Buttigieg claimed victory, as a technical meltdown severely hampered the reporting of the final results – which are still being hammered out.