PHILADELPHIA, PA — Bernie Sanders, who scored a stunning upset in Michigan's presidential primary last spring, used his sway with the state's delegates at the Democratic National Convention Thursday to convince them to vote for Democratic nominee Hillary Clinton, calling Donald Trump a dangerous demagogue who is unfit to lead the country.

While speaking at a breakfast gathering that also included delegates from Minnesota, Tennessee and Oregon, the Vermont senator made an impassioned plea to his supporters, saying it is "absolutely imperative" that they vote for Clinton to prevent a Trump presidency, according to media reports. "Donald Trump is the most dangerous candidate to run for president in the modern history of this country," Sanders said, unleashing a laundry list of complaints about the New York real estate tycoon, including his participation in the "birther" movement that questioned President Barack Obama's citizenship.

"That was an effort to de-legitimize the election of the first African-American president we have had, based on racism pure and simple," Sanders said. "That type of person must never, ever become president." Seeking to bridge the divide between Clinton and the "Bernie or Bust" movement, newly invigorated by the release of leaked emails on the eve of Democrats' nominating convention, Sanders told his supporters they had pushed the party's platform to the left in a way that recognizes a "grotesque and immoral level of wealth and inequality" in this country.

He reminded supporters that "real change in America never takes place just by electing a president" or in a single election cycle. "It takes place from the bottom up," he said, encouraging younger supporters participating in presidential politics for the first time to remain involved. "We are going to continue to fight for an economy that works for all of our people not just the 1 percent," he said.

But was it enough to move Sanders supporters to the Clinton camp?

Christopher Geiger, 34, a Sanders delegate from Holland, told The Detroit News he's "not there yet."

"What I really want to see is Hillary Clinton talking about the issues," Geiger told the newspaper. "If she keeps talking about the issues, I think a lot of Sanders supporters could eventually get behind her." Lisa DiRado, a Clinton delegate from Northville, told the Detroit Free Press she thinks Sanders' endorsement of Clinton was effective, though he likely didn't persuade all of his supporters.