Vermont Sen. Bernie Sanders, an independent, highlighted some of the Biden-Harris accomplishments they made since coming to the White House in the midst of the COVID-19 pandemic, from expanding Medicaid to providing rent relief and mortgage relief to protecting union workers' pensions.

"When the political will is there, government can effectively deliver for the people of our country," he said. "We need to summon that will again -- because too many of our fellow Americans are struggling every day to just get by -- to put food on the table, pay the rent, and get the health care they need."

"Bottom line: We need an economy that works for all of us, not just the greed of the billionaire class," he said to applause.

He said, though, that more needs to be done and laid out a progressive agenda. At the top of that to-do list, he said, is to "get big money out of our political process." He called for the "disastrous Citizens United Supreme Court decision" to be overturned, as well as increasing the minimum wage and more prescription drug cost cuts.

"I look forward to working with Kamala and Tim to pass this agenda," he said. "And let us be clear. This is not a radical agenda. But, let me tell you what a radical agenda is. And that is Trump’s Project 2025. Giving more tax breaks to billionaires. Putting forth budgets to cut Social Security, Medicare and Medicaid. Letting polluters destroy our planet. That is what is radical. And we won’t let it happen."

He also called for an immediate cease-fire in Gaza and the return of hostages, to applause from the crowd.

Sanders, who was slower to endorse Harris for the presidency, ran for president himself in 2016 and 2020.

In his remarks, Senate Majority Leader Chuck Schumer praised Vice President Harris and said she will need a Democratic majority if she wins the presidency.

"She can't do it alone," he said.

Schumer predicted Democrats will perform well this November, calling back to the "red wave" prediction that didn't materialize in 2022 and listing candidates he said are strong in closely-watched races in Montana, Arizona and Maryland.

"Ladies and gentlemen, my good friends at this convention: I am telling all of you now we're going to hold the Senate again and we're poised to pick up seats," he said.

Schumer served alongside Harris in the Senate.

Behind Enemy Lines, a pro-Palestinian group, gathered early evening Tuesday in front of the Consulate of Israel in downtown Chicago.

Initially there was a small group of about 25 people, but the numbers grew within an hour -- enough for police in riot gear to hold a formation to prevent the group from moving farther down the block.

Behind the police line stood a pro-Israel group of about 100 demonstrators holding flags. Both groups were aware of the other and, at one point, each pressed against the police line from both sides.

No clashes took place.

Around 8 p.m. local time, the Israel group started dispersing.

At least five people were seen being taken into custody. The police didn't initially report any arrests.

Chicago Police Superintendent Larry Snelling was seen standing among the officers.

-ABC News' Mark Guarino

Harris addressed the DNC crowd from a rally in Milwaukee and thanked the delegates for nominating her as the Democratic presidential nominee.

Harris spoke at the Fiserv Forum, where Trump accepted the nomination last month.

"This is a people-powered campaign, and together we will chart a new way forward," she said.

Read more about the Harris campaign's decision to hold a rally in the battleground state of Wisconsin on the same night as the DNC here.