Donald Trump is facing a fierce backlash for questioning the race of US election rival Kamala Harris, but to those acquainted with the Republican's long history of inflammatory language and behavior around the issue, the smear was nothing new.

Trump's political career was forged in the cauldron of the 2010s "birther" conspiracy theory that sought to delegitimize then-president Barack Obama -- who had a Kenyan father -- by claiming falsely that he was born abroad.

Those who say Trump is racist point to dozens of other controversies the property tycoon has stoked, from being sued in the 1970s for discrimination against Black tenants to his notorious pandering to white supremacist marchers in 2017.

Trump's worst impulses resurfaced Wednesday with his outlandish claim that Harris -- the first female and non-white vice president -- recently "became a Black person" for political convenience.

Like an estimated 34 million Americans in the nation's fastest-growing demographic, Harris is mixed race and has been consistent in celebrating her Black and South Asian identity.

The attack handed Trump back a media spotlight that had evaded him since Harris's game-changing entry into the White House race, but it also honed attention on his extensive record of racial transgressions.

"He did crap the bed... The only question is whether he's going to roll around in it or get up and change the sheets," veteran strategist Scott Jennings, a onetime aide to former President George W. Bush, told CNN.

- 'Lion's den' -

Trump's inflammatory comments came amid a barrage of insults and falsehoods as he attacked Harris during a combative interaction with African American journalists in Chicago.

The 78-year-old is desperate to woo Black voters from Harris -- who has erased his polling leads since jumping into the race -- but the invitation was already controversial, given his well-documented history of denigrating Black female reporters.

Jennings suggested that Trump should move on from the scandal, but the former president has been doubling down, sharing images of Harris celebrating her Indian origins as some kind of ill-conceived "gotcha."

Riding high after surviving an assassination bid in July, Trump saw his campaign thrown into chaos when the 59-year-old vice president replaced Joe Biden at the top of the Democratic ticket for the November 5 election.

Keith Gaddie, a politics professor at Texas Christian University, said Trump's motivation for his latest remarks was likely a compulsion to grab back the limelight, as "no one is talking about assassination attempts anymore."

But he also sees significance in the context -- a conversation with three African American interviewers in front of an audience of fellow Black journalists -- and believes the ex-president was playing "the gladiator in the lion's den" for his white base.

"He essentially decided to battle his opponent by proxy, by battling with Black female journalists," Gaddie said.

- 'No sense of decency' -

Bill Kristol, chief of staff from 1989-93 to then vice president Dan Quayle, said Trump's goal was likely to revive old characterizations of Harris as inauthentic after her pivot to the political left during her 2020 primary campaign.

"Trump has no sense of decency. It would be nice if this were disqualifying for political success," Kristol wrote in a newsletter Thursday for center-right publication The Bulwark.

"But decency doesn't always prevail in this world of ours. Decency needs to be aggressively defended. Indecency needs to be exposed and denounced."

While some observers see Trump's racial remarks as part of some clever political strategy rather than the intemperate outbursts of a bigot, analysts are mixed on whether they are helpful.

"Birtherism made him an avatar of populist conservatism in 2011 and his attacks on Mexicans and Muslims played a critical role in his victories in 2016," said Donald Nieman, a political analyst and professor at Binghamton University in New York state.

"They stoke the passion of the base and that's important. But they also turn off a lot of the few swing voters who play a critical role in deciding elections these days -- as the results in 2018, 2020, and 2022 suggest."

Political scientist Nicholas Creel, of Georgia College and State University, told AFP the latest controversy lays bare Trump's lack of self-control and narcissism -- "Trump being Trump" -- rather than some underlying strategy.

"The best way to view this specific scandal is not as some sort of fifth-dimensional chess strategy whereby he was looking to excite his base via dog whistles," he said, "but simply as an insensitive comment from a latently racist old man who thinks he can do no wrong."