"I worked as hard as I could after endorsing Hillary Clinton," Sanders said on NBC's "Meet the Press."
Asked by host Chuck Todd if he accepted Clinton's criticism
that his primary challenge to her and his sustained following helped elect President Donald Trump, the Vermont independent said, "No, I really don't."
Sanders also brought up and rebutted a popular talking point that some of his supporters did not go on to vote for Clinton in the general election. He pointed out that a large portion of Clinton's supporters in the 2008 Democratic presidential primary went on to vote for Republican Sen. John McCain over Democrat Barack Obama.
"You know people say, 'Well, not everybody who voted for Bernie ended up voting for Hillary.' No kidding," Sanders said. "That's what happens in politics."
Sanders also said the re-litigation of the 2016 election was unproductive and that the Democratic Party needed to undergo a fundamental shift.
"The current model of the Democratic Party is obviously not working," Sanders said.
'Medicare for all'
As Clinton began a raft of interviews and appearances to tout her campaign memoir, "What Happened," Sanders spent the week rolling out his proposal to expand government health coverage to all Americans. A group of Democrats, many of them potential
2020 presidential hopefuls, joined Sanders and signed onto his effort.
Sanders batted back criticism that his proposal to replace Obamacare with a single-payer system would help Republicans who pledged to repeal and replace the standing health care law.
"The immediate concern is to beat back these disastrous Republican proposals," Sanders said.
He said his Medicare for all legislation was about making a statement and setting a target for the US to join other nations in having the government guarantee health coverage.
"It's not going to happen tomorrow," Sanders said. "I fully admit that, but we need to put the benchmark down there and go forward."
As for criticism that the program would be too expensive, Sanders said he believed it would reduce expenses on administrative costs relative to private insurance and allow for the negotiation of cheaper drugs. He also countered that an increase in the tax burden would be tempered for many by the elimination of insurance premiums.
"My Republican friends say 'well, Bernie wants to raise your taxes,'" Sanders said. "They forget to conveniently mention that Bernie wants to do away with the private insurance premiums that you're now paying."
Sanders went on to claim his legislation would save money for the average middle-class worker.