Trump, 78, launched a scathing attack on his Democratic rival, as he took the stage for the first time to address an election rally after Harris became the presumptive nominee. 

Over the weekend, President Joe Biden, 81, announced that he was dropping out of the race and named Harris as his successor. 

Harris, 59, is now the presumptive Democratic nominee and she was officially announced as the party's vice presidential candidate at its Democratic National Convention in August. 

"For three and a half years, Lyin' Kamala Harris has been the ultra-liberal driving force behind every single Biden catastrophe. She is a radical left lunatic who will destroy our country if she ever gets the chance to get into office. We're not going to let that happen," Trump said as he unleashed a torrent of attack against the vice president. 

"I was supposed to be nice. They say something happened to me when I got shot. I became nice. And when you're dealing with these people, they're very dangerous people. When you're dealing with them, you can't be too nice. You really can't be. So if you don't mind, I'm not going to be nice. Is that okay?" he asked his supporters amidst huge applause from the audience. 

"Kamala Harris is the most liberal elected politician in American history. She's an ultra-liberal politician. She's absolutely terrible. She's more liberal than Bernie Sanders, he said. If she ever got in, she'd destroy this country so fast. She was the border czar, but she never went to the border," Trump alleged. 

"She was appointed by this horrible president, this horrible guy. How this guy got to be president in his basement. He stayed in his basement. And we did a lot better the second time than we did the first. How this guy got to be president, what they've done to this country in three and a half years, and we're going to turn it around. But what they've done to our country is unthinkable," Trump alleged.