At his first rally since leaving the White House, former President Donald Trump has criticized President Joe Biden and Vice President Kamala Harris over the border crisis.

In front of thousands of supporters at a rally in Wellington, Ohio on Saturday, June 26, the former president blamed Joe Biden on the rising number of immigrants crossing over the U.S.-Mexico border.

"You have millions of people coming into our country. We have no idea who they are. Joe Biden is doing the exact opposite as we did," Trump said as CNBC reported.

Donald Trump noted that the Biden administration is putting American families "into a very very bad position" by letting "all these people coming into our country," Reuters reported.

The former president also criticized Kamala Harris' recent trip to the U.S.-Mexico border. He said the vice president made the trip because he announced that he was visiting the area, The Hill reported.

Donald Trump noted that if he had not announced his scheduled visit to the U.S.-Mexico border, he "don't know if she was ever going to go."

The White House has already denied that the trip of Kamala Harris at the border resulted from Republican criticism. 

Top Harris aide Symone Sanders said the Biden administration does not take their cues from Republican criticism, particularly not from the former president.The White House has called the former president's immigration policies inhumane.

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Donald Trump Hinting Presidential Run

During his speech, Donald Trump also presented the possibility of running for office again in 2024. The former president said the Republicans won the election twice, and it's possible they could win it a third time, CNBC reported.

Donald Trump had won the 2016 election against former Secretary of State Hillary Clinton, while he lost in the 2020 presidential election against Joe Biden.

The former president vowed that they would take back the House, the Senate, and America. He added that they would do it soon.

Ohio Rally Supporters

Many are still supporting Donald Trump, with one supporter saying that she thinks he is the true president. According to Buzzfeed News, many came to the Ohio rally with their red hats with the words "Make America Great Again" and pro-Trump shirts and some representation of the American flag.

More than half of Republicans think the election was rigged, while 53 percent think Donald Trump is the actual president, according to an Ipsos/Reuters poll in May.

Meanwhile, only 30 percent of Republicans feel confident that absentee or mail-in ballots were accurately counted compared to 86 percent of Democrats and 55 percent of Independents.

Eighty-seven percent of Republicans think it is vital that the government place new limits on voting to protect elections from fraud.

When they took the stage in the Ohio rally, some notable Republican lawmakers such as Georgia Republican Rep. Marjorie Taylor Green chimed in false claims that Democrats stole the elections.

Greene said that Donald Trump should be the nation's president now, but the Democrats "stole the election."

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WATCH: Former President Trump Visits Northeast Ohio For "Save America" Rally - From WBNS10 TV