WASHINGTON (AP) — Sen. Elizabeth Warren is on the verge of launching a presidential campaign that should be all about her vision for the future. But first she has to explain her past.

For the second time in two weeks, the Massachusetts Democrat apologized Wednesday for claiming Native American identity on multiple occasions early in her career. The move followed a report that she listed her race as “American Indian” — in her own handwriting — on a 1986 registration card for the Texas state bar.

By providing fresh evidence that she had personally identified her race, the document resurrected the flap just as she’s trying to gain momentum for her 2020 presidential bid, which she’s expected to formally announce on Saturday. Warren didn’t rule out the possibility of other documents in which she identified as a Native American.

In a Democratic primary already dominated by candidates expressing remorse for past actions, Warren’s repentance stood out, both for the distraction the controversy has become for her candidacy and the complexity of her efforts to move beyond it. While her competitors are fine-tuning their messages and trying to demonstrate competence and polish, Warren has repeatedly opened herself up to criticism by relitigating the past.

“It’s not exactly how you’d want to enter the arena” as a presidential candidate, said Paulette Jordan, a former Democratic state representative in Idaho and a member of the Coeur d’Alene Tribe who became the party’s gubernatorial nominee last year. Jordan warned that Warren’s treatment of her heritage raises “a whole lot of questions and doubt” about her integrity: “If you cannot uphold that, then it makes things challenging.”

Questions about Warren’s heritage date to at least 2012, when her Republican opponent seized on the issue during her first Senate campaign to wrongly argue she identified as a Native American to advance her career. President Donald Trump frequently deploys a racial slur to criticize Warren.

Still, Warren has sometimes compounded the problem. In October, she released a DNA analysis that purported to bolster her claims to Native American heritage. Instead, it drew quick criticism from some Native Americans, including a Cherokee Nation official, as insensitive and fumbling.

She apologized in private last week to the principal chief of the Cherokee Nation for “causing confusion on tribal sovereignty and tribal citizenship and the harm that resulted,” said tribal spokeswoman Julie Hubbard. And after The Washington Post reported on the Texas state bar registration, Warren addressed the issue publicly Wednesday, telling reporters outside her Senate office that her answers in the past were “based on my understanding of my family’s story.”