Sen. Bernie Sanders, I-Vt., argued Sunday that among the presidential candidates, he was the best Democrat to win back a string of Midwestern states from President Trump in 2020, claiming that the sitting president had told working-class families a "monstrous lie" by vowing to take on monied interests in Washington.

"Donald Trump has told literally thousands of lies since he began his campaign and since he has been in the White House," Sanders told an estimated crowd of 4,500 at an outdoor rally in Pittsburgh. "But, the biggest lie that he told the people of Pennsylvania ... was that he was going to stand up for working families and take on the establishment."

Sunday's rally wrapped up a four-day, five-state swing during which Sanders also held rallies in Wisconsin and Michigan. Voters in all three states backed Trump over Hillary Clinton in 2016, stunning Democrats who had seen them as part of a "blue wall" held together by urban African-American voters and traditionally liberal white working-class voters. The Sanders campaign said in a memo prepared in advance of the trip that the pathway to victory runs through the Midwest.

The memo said that Sanders has received donations from more than 8,000 people in Wisconsin, 14,000 in Michigan and 18,000 in Pennsylvania. Sanders was leading all Democratic candidates in fundraising.

Sanders had a good showing in the industrial belt in 2016's Democratic primary, winning Michigan, Indiana and Wisconsin. But Hillary Clinton pounded him by 12 percentage points in Pennsylvania.

"We are going to win in Pennsylvania, we’re going to win in Michigan, we're going to win in Wisconsin, we're going to win in Indiana and Ohio," Sanders promised his cheering supporters. "And, by the way, we’re going to win the election."

Earlier in Lordstown, Ohio, and again in Pittsburgh, Sanders pressed Trump to put action behind his words on General Motors plant closings. Trump has assailed the company for shutting its small-car factory in Lordstown, in a politically important state, complaining about the company's leadership and a local union leader while seldom mentioning the other U.S. factories that GM plans to close.

That's not enough, Sanders said.

"If you want a federal contract paid for by taxpayers, treat your workers with respect and dignity. No more paying your workers inadequate wages while you provide CEO's with multimillion-dollar parachutes, no more taking away health care benefits, no more denying workers the right to form a union.

"And if you are not a good and responsible corporate citizen, do not think that you will get federal contracts," Sanders added.

The self-described democratic socialist said his political movement mirrored the labor movement, the civil rights movement, the women's movement and the gay rights movement in showing that "real change never takes place from the top on down, always from the bottom up." He recited a laundry list of policies -- including raising the federal minimum wage, government-run health care and legalizing marijuana -- that he claimed were described as "too radical" by members of the media and political establishment.

SEN. BERNIE SANDERS: WE NEED AN ECONOMY AND GOVERNMENT THAT WORKS FOR ALL, NOT JUST THE TOP ONE PERCENT

"Today, virtually all of those ideas are supported by a majority of the American people and they are ideas that Democratic candidates from school board to president of the United States now support," Sanders said, noting that his insurgent campaign for the 2016 Democratic nomination had netted "more votes from young people than Trump and Clinton combined."

Sanders also proudly noted that his supporters had campaigned successfully to change the party's rules governing superdelegates at next year's Democratic National Convention "and maybe ending a system in which one candidate had 500 superdelegates before the first vote was cast." The Democratic National Committee voted last summer to prevent superdelegates from voting on the first presidential nomination ballot unless a candidate had enough votes from pledged delegates, who choose a candidate based on the results of the Democrats' primaries and caucuses.

The Vermont senator also addressed his signature issue, vowing to health insurance companies that "whether you like it or not, the United States will join every other major country on earth and guarantee health care to all people as a right."

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"It is an international embarrassment that in America today we got 30 million people with no health insurance and even more who are underinsured with high deductibles and high co-payments and for all of that we end up spending twice as much per capita on healthcare as do the people of any other nation," said Sanders, who warned his audience that "the insurance companies are getting nervous" about his message.

"They are prepared and will spend hundreds of millions of dollars to stop us," he said, "but we are gonna win this struggle and we will pass a Medicare for All single-payer program."

Fox News' Jennifer Oliva in Pittsburgh and Adam Shaw contributed to this report.