Actor Rob Lowe deleted a tweet mocking Sen. Elizabeth WarrenElizabeth Ann WarrenJulián Castro is behind in the polls, but he's finding a niche Gabbard arrives in Puerto Rico to 'show support' amid street protests Democratic strategist predicts most 2020 candidates will drop out in late fall MORE (D-Mass.) over her past claims of Native American ancestry.

“I deleted my Elizabeth Warren tweet,” Lowe tweeted late Saturday night. “It was a joke and some peeps got upset, and that’s never my intention.”

“On the GOOD side: I just got to use the Oxford comma!” he added.

Lowe’s tweet did not use an Oxford comma, which appears in a list of three or more items separated by commas.

Earlier Saturday, the “West Wing” actor wrote in the now-deleted tweet that Warren running for president “would bring a whole new meaning to Commander in 'Chief.’”

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Warren, who officially launched her 2020 campaign on Saturday, has come under fire for identifying herself as Native American in the past. Last week she apologized and clarified that she understands the difference between tribal citizenship and a DNA test indicating Native American ancestry.

President TrumpDonald John TrumpUS-Saudi Arabia policy needs a dose of 'realpolitik' Trump talks to Swedish leader about rapper A$AP Rocky, offers to vouch for his bail Matt Gaetz ahead of Mueller hearing: 'We are going to reelect the president' MORE, who has repeatedly mocked Warren over her claims, called out the Democrat again in a tweet Saturday, and appeared to reference the Trail of Tears forced relocation of thousands of Native Americans.

"Today Elizabeth Warren, sometimes referred to by me as Pocahontas, joined the race for President,” he wrote. “Will she run as our first Native American presidential candidate, or has she decided that after 32 years, this is not playing so well anymore? See you on the campaign TRAIL, Liz!”

--This report was updated at 10:29 a.m.