She’s planning to run for president, and she’s trying to get out from whatever attacks Trump and other opponents may throw her way.

That’s the inescapable conclusion from Sen. Elizabeth Warren (D-Mass.) releasing a DNA test Monday suggesting that she has distant Native American ancestors. But could her DNA test backfire on her efforts to get out from under this years-long controversy?

This story goes back to her first major political campaign, and it’s one President Trump — knowing full well Warren may challenge him in 2020 — hasn’t let go of. He tweeted about it three times Tuesday morning alone.

Since this debate probably isn’t going anyway anytime soon, here’s a primer on what happened.

How this all got started: When Warren was first running for Senate in 2012, the conservative newspaper the Boston Herald reported that her employer, Harvard University, touted her Native American heritage in the ’90s to show off the diversity of its faculty. At one point, the school newspaper referred to Warren as “the first woman with a minority background to be tenured.”

Warren’s campaign staff didn’t have documentation on hand. “Like most Americans, Elizabeth learned of her heritage through conversations with her grandparents, her parents, and her aunts and uncles,” her campaign said.

But Warren also said she didn’t approve the school using her background to talk about minority status and that she didn’t remember talking about her heritage with the school, especially during the hiring process. Other officials at the school backed her up that her heritage wasn’t part of hiring conversations.

So how did the school find out about her heritage? A former Ronald Reagan appointee who helped hire Warren told the Boston Herald when it broke the story that he asked her about it well after she got the job after seeing a picture of Warren’s mother and asking her about it.

But Warren had a role in this, too: Journalists in Boston started uncovering evidence that suggested that Warren may have known more about Harvard’s promotion of her as Native American than she first let on.

Warren had actually been identifying as a minority for nearly a decade in an official national law school directory, the Association of American Law Schools desk book. And the Boston Globe also reported that for at least six years, Harvard University reported to the federal government that it had a Native American law professor. It was a statistic the paper argued was probably reported by Warren herself to the school.

The closest Warren got to acknowledging that she proactively listed herself as Native American at work was when she said she put her heritage in that national directory in hopes of finding other professors across the country with similar backgrounds: “I listed myself in the directory in the hopes that it might mean that I would be invited to a luncheon, a group, something that might happen with people who are like I am. Nothing like that ever happened, that was clearly not the use for it, and so I stopped checking it off,” she said.

How this played out in the 2012 Senate campaign: Warren’s heritage was one of its signature controversies, amplified by the national attention the race received. Warren was trying to unseat Sen. Scott Brown — a Republican anomaly in Massachusetts — and she was one of the Democrats' best efforts to pick up a Senate seat that year.

Brown’s campaign pounced on this, but they arguably overplayed their hand. Brown’s campaign demanded that Warren apologize for letting Harvard hold her up as a minority decades ago. Warren refused, saying she was proud of her family’s heritage and reiterating that it didn’t help her get a job.

“I believe that I was recruited at Harvard because I’m a good teacher and recruited for my other jobs because I do good work,” she said.

Then, two Republican staffers handed Warren a political gift by doing tomahawk chops at a rally, and the story shifted to how Brown should condemn that kind of behavior. (He did.)

In a Boston Globe poll taken in the thick of the weeks-long story, most voters said the controversy wouldn’t affect their vote. But Warren’s unpopularity spiked, with three times as many voters saying they disliked her.

Why this is a big deal now: Because Trump hasn’t let it go. And like Brown’s campaign in 2012, Trump has stepped in it in a way that’s handed Warren some leverage. He repeatedly insults Warren as “Pocahontas,” undermining his own argument that Warren is the one using Native American culture for political benefit.

He also promised — then denied he ever promised — that he’d pay $1 million to charity if she could prove her ancestry. When asked about it Monday, Trump said he’d donate only if he “can test her personally.”

But Warren’s DNA test could backfire for her: Warren wanted to put Trump’s attacks at rest by taking this test. But it’s possible that her move only stirred up the controversy. The Cherokee Nation, which in 2012 mostly stayed out of the furor, said it was “inappropriate” for Warren to claim a connection to the tribal nation — most likely aware of how this could be a major campaign issue in a few years and unwilling to be drawn into it.

Plus, the DNA test suggests that Warren has Native American ancestry from many generations ago, distant enough to allow Republicans to plausibly slice and dice the numbers to argue that her heritage is minimal. (And they have.)

Trump certainly sees political benefit in making this a story. The unanswered question is how this will play out for Warren now that she, too, has elevated it.