Trump was introduced to the stage by Melania in an unannounced appearance.
The race for the White House remained essentially a dead heat on Sunday -- with nine days to go until Election Day.
Former President Donald Trump delivered a speech Sunday afternoon at New York's Madison Square Garden. After making several stops in Philadelphia on Sunday, Vice President Kamala Harris held a rally there Sunday afternoon.
Almost 42 million Americans have cast a vote through early voting methods, as of Sunday afternoon, according to data from the University of Florida's Election Lab.
The about 41.9 million recorded mail and early in-person votes were evenly split with about 21 million mail ballots returned nationally and about the same cast at in-person early voting polling sites across the country, the data showed.
Early voting options are now open to voters in 50 states and the District of Columbia. Many early voting periods will last until the weekend before Election Day.
As of 4:30 p.m. ET on Friday, more than 35 million Americans have voted early, according to the Election Lab at the University of Florida.
Of the votes cast, 16,080,81 were in-person early votes and 18,959,123 were mail-in ballots.
This means that more than 20 million people have voted since Monday.
Harris will go after Trump in her speech in Houston, Texas, on Friday night that will focus on reproductive rights.
"The Attorney General of Texas is suing the United States Government so that Texas prosecutors can get their hands on the private medical records of women who leave the state to get care," Harris will say, according to released excerpts of her speech.
"So, see what is happening: Donald Trump won’t let anyone see his medical records. But these guys want to get their hands on yours? Simply put: They are out of their minds," she will say.
The vice president will reiterate her campaign pledge to push Congress to pass a bill restoring Roe v. Wade if elected.
"We are fighting for an America where, no matter who you are, or where you live, you can make that decision based on what is right for you and your family," Harris will say.
ABC News' Gabriella Abdul-Hakim, Fritz Farrow and Will McDuffie
Speaking to reporters before her event later today in Houston, Harris said she wanted to address Trump's comment that America has become a "garbage can" and "dumping ground" for migrants from around the world.
"You know, it's just another example of how he really belittles our country," Harris said. "This is someone who is a former president of the United States, who has a bully pulpit, and this is how he uses it, to tell the rest of the world that somehow the United States of America is trash."
"And I think, again, the president of the United States should be someone who elevates discourse and talks about the best of who we are and invest in the best of who we are, not someone like Donald Trump, who is constantly demeaning and belittling who the American people are," the vice president added.
Trump's comments are the latest example of his anti-immigrant rhetoric.
-ABC News' Will McDuffie
In what could have been his final financial event of the campaign, Tim Walz, at a fundraiser in Pennsylvania, said it was now time to use all that money to focus on the ground game.
"Now it's time to execute ... Never in my lifetime, would I have believed that the choice would be so stark," he said.
The Harris campaign and the Democratic National Committee entered the final three weeks of the election with a clear cash advantage over the Trump campaign and the Republican National Committee, latest FEC records show.
As of Oct. 16, the Harris campaign, the DNC and their joint fundraising committees reported having nearly $270 million in cash on hand compared to $202 million the Trump campaign, the RNC and their joint fundraising committees had in the bank, the new filings show.
The Trump campaign committee, in particular, had $36 million in the bank as of Oct. 16 compared to the Harris campaign committee having $119 million in cash on hand.
-ABC News' Isabella Murray and Soorin Kim
