Sen. Bernie Sanders, I-Vt., had a billionaire in his sights at a campaign rally in Iowa Saturday night -- and for once, it wasn't President Trump.

“Tonight we say to Michael Bloomberg, 'Sorry, you ain’t gonna buy this election,'" Sanders told a crowd in Coralville, outside Iowa City. " ... Those days are gone."

Bloomberg, the former mayor of New York City, qualified Friday to get on the ballot in Alabama, which holds its Democratic presidential primary on March 3, 2020, a date known as Super Tuesday. His team is also making plans to file in Arkansas, which has a Tuesday deadline and also holds its primary March 3.

Sanders also excoriated Bloomberg for avoiding the earliest states on the primary and caucus calendar and focusing his efforts on the states that hold nominating contests on Super Tuesday and later in 2020.

“You’re not going to get elected president by avoiding Iowa, New Hampshire, South Carolina, and Nevada," Sanders said. "Yes, we don’t have a super PAC and I’m not worth $52 billion."

The billionaire businessman initially ruled out a 2020 run, but began to reconsider in recent weeks, citing concerns about the ability of the current crop of contenders to defeat Trump.

Now, the Sanders campaign is fundraising off the news. An email to supporters started off this way: "Did you see the news? Mike Bloomberg is filing paperwork to run for President of the United States. Just what America needs...another billionaire using his wealth to try to buy an election."

Bloomberg won two New York City mayoral elections as a Republican before winning a third term as an independent in 2009. In 2018, he switched his party affiliation to Democrat, saying he was "far away" from the Republican Party and wanted Democrats to provide the "checks and balances our nation needs so badly."

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At an earlier campaign stop in Iowa Saturday, Rep. Alexandria Ocasio-Cortez, D-N.Y., appeared to refer to Bloomberg when she complained of candidates "trying to completely purchase our political system [by] running as Republicans and now tossing in their hats as Democrats in the field as well."

"But what we're here to say is that in a democracy, it shouldn't matter how much money you have, what should matter is whether you vote, whether you caucus when you turn out," she went on. "It's the numbers. It's the people. It's a movement."