Sen. Bernie Sanders disparaged former Mayor Pete Buttigieg for courting billionaire donors at Saint Anslem College on Friday, then doubled down on his remarks on Twitter.

Driving the news: Sanders and Buttigieg both claimed wins in the Iowa caucuses — a major test of 2020 candidates' voter appeal — on Thursday, despite evidence of inaccurate and error-riddled results reported by AP and the New York Times.

What he's saying: Sanders read headlines from Forbes, The Hill and other media outlets that he brought to his campaign stop, claiming that Buttigieg gets outsized financial support from the wealthy.

"I like Pete Buttigieg, nice guy. But we are in a moment where billionaires control not only our economy, but our political process," Sanders said.

He also called out former New York Mayor Michael Bloomberg for "spending hundreds and hundreds of millions of dollars to buy the election."

By the numbers: Sanders raised more money from individual donors in the fourth quarter than all other Democratic candidates, per Five Thirty Eight. 55% of Buttigieg's fundraisers were "big donors," or people who gave more than $200, while 32.4% of Sanders' donors gave over $200.

Businessman Deval Patrick and former Vice President Joe Biden had the most big donors last quarter among their competitors.

The other side: The Buttigieg campaign responded to Sanders by pointing to his Thursday appearance on "The Late Show with Stephen Colbert," per The Hill. Buttigieg promised to use campaign contributions of all amounts to defeat President Trump.

Go deeper: The Sanders surge shapes the Iowa caucuses