Organizers of the 2020 Democratic convention in Milwaukee are on notice: If Bernie Sanders is the party's presidential nominee, he'll ban corporate contributions for the event.

Sanders made the pledge Monday with the release of his plan to "get corporate money out of U.S. politics."

The independent U.S. senator from Vermont has been off the campaign trail since he had a heart attack last week.

Josh Orton, policy director for the Sanders campaign, said: “When Bernie is the nominee, everything will fundamentally change for corporate elites. Bernie Sanders fights for the people, cannot be bought and is under no obligation to fulfill any transaction with a corporation trying to corruptly buy access. A Bernie Sanders convention will be a people-powered convention.”

Even if he becomes the nominee, it's unclear what practical effect Sanders' pledge will have on the Democratic convention.

Milwaukee's host committee has to raise up to $70 million to stage the event. In addition, the Democratic National Convention Committee (DNCC) is aiming to raise another $20 million.

Much of the money is expected to have been raised and spent before delegates arrive, July 13-16.

Corporate donations are key to the funding of the event.

“Our focus is getting the convention appropriately funded and paid for well in advance so that we can deliver a safe and successful convention that puts our nominee in the best position to beat Donald Trump in 2020," Joe Solmonese, chief executive of the DNCC, said in a statement.

Sanders unveiled a wide-ranging plan on corporate cash that includes mandatory public financing laws for all federal elections and passing a constitutional amendment "that makes clear that money is not speech and corporations are not people."

But the plan also takes aim at how conventions are funded, with the Sanders campaign noting that at the 2016 Democratic Convention in Philadelphia, 17 donors provided three-quarters of the funding.

"As the Democratic nominee, Sanders would ban all corporate contributions to the Democratic Party Convention and all related committees," the release said.

Fundraising for Milwaukee's convention has been overshadowed by the intense pursuit of dollars by the party's presidential contenders.

Last month, Solmonese met with lobbyists in Washington, D.C.

The meeting was first reported by POLITICO, which noted an "awkward pairing" of "representatives for special interests meeting with top Democrats while the party’s leading presidential candidates reject corporate PAC and lobbyist cash."

POLITICO said DNC officials "explained during the meeting how corporations can help foot the bill for the convention, regardless of who the nominee is, addressing some lobbyists’ worries that a crusading left-wing nominee like Bernie Sanders or Elizabeth Warren could try to reject corporate money, embarrassing convention sponsors."

POLITICO also reported on "event packages." For instance, a $300,000 donation provides access to two well-placed hotel rooms near the convention site, Fiserv Forum.

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