Former Vice President Joe Biden unveiled an ethics plan on Monday that directly targets President Trump, accusing him of creating the "most corrupt administration in modern history." It's a sign the Democratic presidential candidate is ramping up his defense ahead of the fourth Democratic debate in Ohio on Tuesday.

Biden, who continues facing questions over his son's involvement in foreign companies while he was in office, istrying to refocus the ethics debate squarely on Trump, his presidency, and his administration.

Biden's proposal comes amid an ongoing onslaught of debunked attacks from President Trump and his GOP allies. The president has falsely said that as vice president, Biden pressured Ukraine to fire a prosecutor in an effort to shield his son Hunter Biden, who was serving on the board of Burisma, a Ukrainian energy company. There has been no evidence of wrongdoing by Joe Biden or his son Hunter, and ousting the prosecutor was in line with U.S. and E.U. policy to encourage more investigation of corruption in Ukraine.

But that has not stopped Trump from doubling-down on the false story.

Biden called out the president by name in his plan and said that Trump has "abused the presidency to enrich himself — spending countless tax dollars at his own properties."

Biden pledged that, if elected, he would enact a wholesale ethics reform that would prevent any future president from abusing the presidency for personal gain.

His plan attempts to limit conflicts of interests and prevent the White House from interfering in federal investigations. It attempts to create a stricter firewall between the White House and the Department of Justice.

Biden's plan would also require candidates seeking federal office to disclose tax returns, going back 10 years. Trump did not release his tax returns in 2016, which was an unusual move in modern politics.

And while much of the focus of this plan could be interpreted as a response to Trump and his presidency, the plan also seems to tackle criticism Biden has received from within his own party.

The plan bars lobbying from foreign governments and calls for a constitutional amendment to eliminate private dollars in federal elections. Essentially, he's calling for the overturn of the Supreme Court's Citizens United decision and for public financing of elections. This echoes legislation Biden sponsored decades ago in the Senate in the 1970s, but it also comes as he's faced criticism from progressive voters for his high-dollar fundraisers this campaign cycle, which rivals Bernie Sanders and Elizabeth Warren have eschewed.

Biden has thus far not received much criticism from his primary opponents about his son Hunter's role in foreign companies. His fellow Democrats have been hesitant to engage in any debate over a perceived a conflict of interest, likely in the fear that they could be accused of feeding into Trump's agenda.

But Biden's ethics plan comes on the eve of the next Democratic debate, and a day after his son Hunter announced via a statement from his attorney that he would be stepping down from the board of a Chinese-backed private equity firm. He also pledged to not engage in business with any foreign-owned companies if his father is elected.

Arecent NPR/PBS Newshour/Marist poll foundthat a plurality of Americans believe Trump's accusations are hurting Biden's prospects of becoming the Democratic nominee.

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