On Saturday, after Senator Elizabeth Warren of Massachusetts formally announced her campaign to oust President Trump from the White House, he took aim at her on Twitter.

“Today, Elizabeth Warren, sometimes referred to by me as Pocahontas, joined the race for President,” he said, making a strange, meta-textual reference to his previous tweets before launching into his usual mockery of Ms. Warren’s claims to Native heritage. “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.”

Most observers took “trail” as a deliberate reference to the “Trail of Tears,” the forced relocation throughout the 1830s of several southeastern Native American tribes from their ancestral lands to what would become northeastern Oklahoma. The strongest evidence for this reading is the reaction from supporters. One pro-Trump tweeter directly mentioned the “Native American genocide.” Trump’s oldest son shared similar comments, calling the jab “savage.”

Lying behind all this is Trump’s fascination with Andrew Jackson. Jackson’s portrait hangs in the Oval Office. He seems to be a figure of admiration for a president who otherwise ignores history. “Inspirational visit, I have to tell you,” Trump said, when he visited Jackson’s mansion in Nashville. “I’m a fan.”