Sen. Bernie Sanders (I-VT) spoke at the National Press Club in Washington, D.C. yesterday and said that President Obama’s biggest mistake was expecting Congressional Republicans to actually negotiate with him, the Huffington Post reported.

“If you were to ask me what his major mistake has been,” Sanders told the crowd, “it’s that he thought that after putting together this extraordinary grassroots movement of young people, minorities and working-class people and getting elected to the presidency, then he thought he could sit down with the Republicans and negotiate all these agreements. He was mistaken.”

According to Sen. Sanders, this mistake is evident in the fact that President Obama hasn’t really been able to pass many of the progressive policies that polls show most Americans actually want.

“The American people say raise the minimum wage; the United States Congress says give tax breaks to billionaires,” said Sanders. “The American people say we have to move towards sustainable and clean energy and energy efficiency, the United States Congress says build the Keystone Pipeline. And on and on.”

Sanders also said this inability to get the GOP to work towards implementing these policies had a detrimental effect on voter turnout, which led to the election of more Republicans who would oppose him.

“If we continue to have elections in which 63 percent of the people don’t vote, 80 percent of young people don’t vote, then the rich will only get richer and will continue to dominate what goes on here in Washington. Any serious president that wants to represent working families has to mobilize people all over this country to make the Congress an offer they can’t refuse.”

The senator also touched on a possible run for president in 2016, saying that he hadn’t yet made up his mind, but that he understood just how much of a struggle his campaign would be.

“[I] don’t want to do this thing unless I can do it well,” said Sanders. “Can we put together the political movement of millions of people who are prepared to work taking on the billionaire class? And that’s what I’m trying to find out. I go around the country and there’s a lot of support for these ideas, more than I think inside-the-Beltway pundits understand. But can you convert that into grassroots organization? How do you raise money?”

“[It] is awfully hard to run as an independent if you are not a billionaire. I am not a billionaire,” he said, adding that mulling over the decision to run is the reason why he’s “getting balder and balder, and grayer and grayer.”

Watch Sen. Sanders’ full speech from the NPC luncheon.