As Sen. Bernie Sanders' fellow presidential rivals made a last-minute appeal for campaign cash ahead of the FEC filing deadline on Tuesday, the Vermont independent issued a statement decrying the money grab as a "national disgrace" and renewed his call to overturn the Citizens United Supreme Court decision that enables such campaign financing.

"It is a national disgrace that billionaires and other extremely wealthy people are able to heavily influence the political process by making huge contributions. The Koch brothers alone will spend more than the Democratic and Republican parties to influence the outcome of next year's elections. That's not democracy, that's oligarchy," Sanders said in a statement.

In the 2010 Citizens United v. Federal Election Commission Supreme Court case, the court ruled that independent third-party political expenditures by corporations and unions, including non-profit corporations, are considered free speech protected under the First Amendment and cannot be restricted by the government, explains the American Civil Liberties Union. The ruling resulted in a tremendous increase in political spending and allowed for the creation of super PACs that can spend unlimited amounts of money on the election or defeat of a candidate, as long as it remains an independent venture and no direct contributions are made to the candidate.

Sanders has repeatedly called for a constiutional amendment to undo that ruling, and has pledged to only nominate judges who would support overturning it, according to The Hill.

"Elections should be determined by who has the best ideas, not who can hustle the most money from the rich and powerful," Sanders added. "Unless we end this disastrous campaign finance system, our government will continue to represent the interests of the few at the expense of the many."

The self-described democratic socialist has also pledged not to accept support from a super PAC, calling other candidates' "mad scramble" for super PAC money appalling. As Politico notes, some progressives have said his super PAC decision could hurt his presidential chances.

A number of candidates held last-minute fundraisers ahead of Tuesday's FEC deadline. Democratic presidential front-runner Hillary Clinton was in New York City the last two days raising money, while Florida Republican Sen. Marco Rubio was raising money in southern California on Tuesday and Kentucky Republican Sen. Rand Paul was in Denver, according to Politico.

Sanders sent an email to supporters asking for $3 donations prior to releasing his statement, noting that his campaign has received more than 200,000 donations so far. According to FEC filings from the organization handling his digital donations, Sanders has raised rougly $8 million online so far. His aides said they will evaluate when to release their total fundraising numbers this week, according to CNN.

Clinton's campaign revealed Wednesday that she has raised a record $45 million in political contributions since announcing her bid for the White House in April, The Washington Post reported.