Bernie Sanders flatly rejected the idea that he played any role in costing Hillary Clinton last week's election, telling an audience in Washington, D.C. Wednesday night that he actually made her a better candidate and possibly could have beat Donald Trump himself.

"I say to those critics, number one, that you can argue the exact reverse, that maybe I would have been elected President of the United States," he said to cheers while being interviewed by Washington Post columnist E.J. Dionne on stage at George Washington University.

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Sanders appeared at the event to promote his new book, "Our Revolution: A Future To Believe In," and give what a group affiliated with the Vermont senator billed as a "major speech" about the future of the country under a Trump presidency, which he delivered before the question and answer portion.

In the speech, he called for working with Trump on populist issues like infrastructure spending while opposing the president-elect on what Sanders called racism, sexism and bigotry.

During the Q&A after the speech, Dionne pressed the former presidential candidate on criticism that he damaged Clinton during their primary campaign by drawing out the race and telling supporters that his rival was corrupt and that the system was rigged.

Sanders rejected the notion out of hand. "The presumption behind that question is, I guess, we should anoint candidates for president," he said, noting that stolen emails released by Wikileaks showed the Democratic National Committee was "not a neutral force" in the primary.

U.S. Senator Bernie Sanders leaves after attending the Senate Democrat party leadership elections at the U.S. Capitol in Washington, Nov. 16. CARLOS BARRIA / Reuters

And he argued that the pressure he applied to Clinton made her better equipped to challenge Trump.

"Do I think our campaign, in a sense, made Hillary Clinton a better candidate? Yeah I do," Sanders explained. "And I’ll tell you why, because by the end the campaign she was against the Keystone Pipeline, by the end the campaign she was against the [Trans Pacific Partnership trade deal], by the end the campaign she was for making public colleges and universities tuition free."

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Trump upset Clinton in key state like Michigan and Wisconsin which have traditionally gone Democratic. Sanders beat Clinton in those states, whose contests were held during a particularly acrimonious phase of the primary, leading some commentators to compare Sanders to Ralph Nader, the Green Party candidate who is blamed for spoiling the 2000 election for Democrat Al Gore.

"My campaign brought millions of people into the political process, the overwhelming majority of whom ended up voting for Hillary Clinton," Sanders said, noting he stumped for Clinton in the campaign’s closing weeks. "Very few people in this country worked harder for Hillary Clinton than I did."

But even as he praised Clinton, he said the Democratic Party now faces a fundamental test if it hopes to come back from last week's loss.

"Which side are you on?" Sanders said. "Can you go out and raise substantial sums of money from the wealthy and Wall Street and those powerful special interests then convince the American people you are on the side of workers and the middle class. Or you do you finally have to say we are going to take on the oligarchy?"

"That is a fundamental difference that exists between Bill and Hillary Clinton and myself," he said.

Sanders added that ordinary people need to know the Democratic Party has the guts to stand up to powerful interests. "If we can’t do that, I don’t see much of a future for the Democratic Party," he said.