The personal attacks are straight from a page out of the 2016 presidential campaign playbook. Former President Trump made headlines when he questioned Harris' ethnicity before an audience of Black journalists.
While it helped Trump build his MAGA base eight years ago, will it help him in in November?
"You can't win an election with just hardcore Trumpy Republicans, you need to get the 11% of Republicans that supported Nikki Haley and her 4% or 5% more moderate Democrat," said Pat Brady, former Illinois Republican Party chairman.
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Brady is in the 11% who supported Haley. He and others said identity politics is not going to help Republicans gain independent voters in swing states, especially among suburban women.
"Nobody can tell Donald Trump what to do or say or what to tweet, but this is all based on one thing: winning. This is about elections, and I want Republicans to win," said New Hampshire Gov. Chris Sununu.
In a New York Times op-ed Thursday, Sununu called on Trump and other Republicans to stop the name calling. He worries about the negative effect it will have on down-ballot Senate and congressional races.
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Since Kamala Harris became the presumptive Democratic nominee, some candidates have already made gains in swing states.
"There are swing states of Senate races going on right now. And the Democratic candidate is actually leading in places like Nevada, Arizona," said Jaime Dominguez, professor of political science at Northwestern University.
So, if the polls show Trump starting to lose ground, will he listen and tone it down? Brady doubts it.
"Media attention is Trump's oxygen. If he doesn't get it, he goes crazy. And he does stupid things like he did yesterday," he said.
With the media attention directed to Harris and the Democratic National Convention this month, some political experts say Trump's rhetoric may become worse.