RICHMOND, Va. -- Donald Trump, the presumptive Republican presidential nominee, issued a new warning to President Obama on Friday as he went after old enemies like Hillary Clinton and Elizabeth Warren at his first campaign rally since the end of the Republican and Democratic primary contests in Richmond, Virginia.

Back to his teleprompter-free self after enduring over a week of criticism from his own party over his attacks against a Hispanic judge, Trump assailed the president's plans to campaign alongside Clinton, the presumptive Democratic nominee, on Wednesday in Wisconsin.

"We have a president that doesn't know what the hell he's doing, folks," Trump said. "I hear he's going to take a lot of time, during our time, when he's supposed to be looking at trade and the military and all of these things, and he's going to campaign for Crooked Hillary."

"You know what? That's OK. That's OK," Trump said before then issuing a veiled threat to the president. "Because if he does that, we're allowed to say things about him that normally we wouldn't bring up. Remember when Bill started campaigning?"

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That was a reference to Trump's willingness to attack Clinton by alleging sexual misconduct on the part of her husband, former President Clinton, in ways that go beyond the usual political back and forth.

Throughout the night, Trump attempted to portray Hillary Clinton as corrupt. In one instance, he told the crowd: "She and her husband hate Obama. Everybody knows it. Right now she's like, 'Yes, sir. No, sir. How should I vote?' She's petrified because she doesn't want to go to jail. The system is rigged. Bernie found it out."

The controversy over Trump University and U.S. District Judge Gonzalo Curiel, who's presiding over a civil suit concerning the educational venture, appeared to weigh on Trump even though he didn't directly mention either.

During his speech in Washington, D.C., earlier in the day, Trump made a pitch toward racial harmony.

"You know, I have the theme, 'Make America great again,'" Trump said. "And I have added a couple of things. I am adding 'Make America great--' right now, I am adding it, 'Make America great again,' I am adding 'for everyone' because it's really going to be for everyone, not going to be for a group of people. It's going to be for everyone."

Later, while admonishing the "poor sad people" of the Never Trump movement, Trump said, "I'm the least, just so you know, I am the least racist person, the least racist person that you've ever seen, the least. I mean, give me a break. But they are saying, 'Is Donald Trump a racist?' I am the least racist person that you've ever looked at."

Five minutes before that proclamation, Trump was going after Warren, the Democratic senator from Massachusetts, calling her "Pocahontas" in reference to her Native American ancestry and a controversy she faced in 2012.

Trump also described Warren as "the worst" and "goofy." He joked that by calling her that, he was doing a "such a disservice to Pocahontas," the actual historical figure. Trump's repeated usage of that name for Warren has been controversial with critics saying the term is a racist slur.

Warren, a possible running mate for Clinton, met with the former secretary of state on Friday. Trump reacted by saying, "I hope she's gonna to be chosen by Hillary. Oh would that be great. I would love it. I would love it."