Bernie Sanders is sharpening his attack on big money influences in politics, taking aim at Super PACs and the Koch brothers in a speech Friday at Southern Illinois University in Edwardsville.

Speaking before a packed Vadalabene Center, the Democratic presidential candidate railed against Republican super-funders who have been accused of tilting elections and lining the pockets of politicians.

“Democracy is not about the Koch brothers and a handful of billionaires spending $900 million in this campaign cycle,” he said (via the Belleville News Democrat). “That is more money than either the Democratic or Republican parties is spending. When you have a situation where one family is spending more money than either of the major political parties, that’s not democracy. That is OL-I-GAR-CHY, and we’re going to change that.”

This is not the first time Bernie Sanders has taken aim at billionaire brothers Charles and David Koch. In his fight for campaign finance reform, he has often singled them out as the face of a corrupt political system.

In August, Sanders railed against the Koch brothers at a South Carolina rally, calling them “greedy billionaires” and pledging that as president, he would aim to overturn the controversial Citizens United decision in which the Supreme Court allowed corporations and wealthy individuals to spend unlimited money in campaigns.

“We live in a nation in which a handful of very, very wealthy people have extraordinary power over our economy and our political life and the media,” Sanders told the packed crowd in Charleston (via The Associated Press).

“They are very, very powerful and many of them are extremely greedy,” he continued. “For the life of me, I will never understand how a family like the Koch brothers, worth $85 billion, apparently think that’s not enough money.”

His remarks came one day after the powerful conservative Super PAC Americans for Prosperity met with Republican presidential candidates.

The attacks on Super PACs and the Koch brothers this week show that Bernie Sanders is refusing to back down despite a string of losses to Hillary Clinton that have made his path to the Democratic nomination steep.

Sanders has a number of weaknesses that his campaign has been working to address, including his performance among non-white voters, but he has shown no signs of giving in. The New York Times noted that even with a big deficit, Sanders could remain in the race for a long time.

“None of this means that the race ends quickly,” the report noted. “Democratic delegates are awarded proportionally, so Mrs. Clinton would need time to clinch a majority of pledged delegates. Mr. Sanders has a loyal base of supporters who could easily fund an insurgent campaign well past the point when it is even plausible to suggest he could win the nomination.”

The appearance on Friday was an important one for Bernie Sanders, who trailed Hilary Clinton by 19 points in Illinois in a recent poll by the Paul Simon Public Policy Institute at SIU-Carbondale. Sanders and his supporters aim to cut into that lead before the March 15 primary, and the location in Edwardsville also helped Sanders pull in voters from neighboring Missouri, Fox 2 Now in St. Louis reported.

Millions of children in this country are not receiving the quality early education that they need. #BernieInIL pic.twitter.com/lWUB2mbafY — Bernie Sanders (@BernieSanders) March 4, 2016

There is another important reason for Bernie Sanders to stay in the race. Even if he does not win the Democratic nomination, his is the only voice in the campaign speaking out in favor of campaign finance reform and a number of other issues closest to working-class Americans. The longer he stays in the race, the more it forces Hillary Clinton to address these issues and ultimately adopt some of these stances to win over the more left-leaning voters in November.

[Image via Instagram/Bernie Sanders]