Donald Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE brushed off Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE's tepid support of him and advice that fellow party members should follow their conscience in voting.

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"He's got to do what he's got to do," Trump said in an interview with NBC News Friday.

Trump repeated his stance that Republicans who are speaking out against him should keep silent.

"If they can't stay positive they should probably not say anything at all because I'm going to win the race," Trump said.

Reports surfaced this week that former President George W. Bush, who hasn't endorsed Trump, is campaigning for vulnerable senators.

"I think he's doing it for whatever reason. I love that he's helping other Republican senators," Trump said.

But he also threw in a dig at former rival Jeb Bush.

"I think he's perturbed by the fact that his brother did very poorly against me," he said. "He can't be thrilled by that."

Trump also shrugged at his recent fundraising efforts after a self-funded primary run.

"They come to me," Trump said of donors.