Sen. Bernie Sanders, I-Vt., on Tuesday rallied supporters behind Democratic nominee Joe Biden, telling them that the day after Biden is elected they will “mobilize our people” to bring about “transformative change.”

“Let’s get going, let’s defeat Trump, let’s elect Biden, let’s elect some great candidates around the country,” he said at a “United Against Trump” livestream event. ”The day after Biden is elected, let us mobilize our people to create the kind of government and America we know we can become.”

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In his remarks, he claimed victory, saying they are “winning the ideological struggle” -- noting that ideas like free college, $15 minimum wage, and immigration reform are now part of the Democratic mainstream.

Many Sanders supporters, and those in the Democratic Party’s left flank, were disappointed in Biden as the nominee, raising fears that they won’t vote and will hand Trump a victory.

But Sanders has worked to bring progressives on board, forming a Unity Task Force with Biden to come up with policy recommendations and vocally supporting his former primary rival.

In a speech to the Democratic National Convention Monday, Sanders praised Biden for incorporating ideas from the more progressive wing of the Democratic Party into his platform and for working with Sanders on issues like climate change.

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“Joe will rebuild our crumbling infrastructure and fight the threat of climate change,” Sanders said. “He has a plan that will greatly expand health care and cut the cost of prescription drugs… Joe will end private prisons, cash bail, the school-to-prison pipeline.”

Sanders added: “Joe Biden will end the hate and division that Trump has created. He will stop the demonizing of immigrants, the coddling of white supremacists.”

He tried to focus his supporters on defeating Trump, something he did again Tuesday, but he also recognized their differences.

“Our job in the next 80 or so days is to do everything that we can to defeat Trump and elect Joe Biden. Do we have differences with Joe Biden? Believe you me, of course we do,” he said. "And our job is, the day after Biden is elected, is to mobilize our people in the fight for a progressive agenda."

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“If we can elect Biden, if we can turn the Senate Democratic, and there is a reasonable chance we can do that, if we can retain Democratic control of the House….if we can do that, there is a path open for us to really bring about transformative change in this country because these people -- Democratic leaders -- are going to have to listen.”

Fox News’ Andrew O’Reilly contributed to this report.