Elizabeth Warren is neck-and-neck with longtime front-runner Joe Biden in Democratic presidential primary polls, but her new status has put a political target on her back.

Questions regarding Warren's claim she lost a teaching job for being pregnant, a central pillar of her personal narrative about why she's seeking the White House, are the senior senator from Massachusetts' first brush with controversy during the 2020 cycle since bungling the release last year of a DNA test she took to bolster assertions she's part Native American.

The questions mark a shift in the dynamics of the crowded field. Biden's dominance and her decision to avoid directly attacking other candidates — other than a swipe at John Delaney during the Detroit debate for launching a presidential bid to "talk about what we can't do" — had shielded Warren from criticism.

Now Democratic operatives are warning the 70-year-old former Harvard Law School professor and Wall Street regulator to brace for more strikes.

“She certainly should expect more specious attacks like this from the Republicans because Warren is the clear front-runner now,” strategist Steve Murphy told the Washington Examiner. “Democrats wouldn’t tolerate a false personal attack from one of their candidates.”

In her stump speech, Warren often says she lost her job as a special needs public school teacher in New Jersey because, at the age of 22, she was about to have her first child with her first husband, Jim Warren.

"By the end of the first year I was visibly pregnant, and the principal did what principals did in those days: wished me luck and hired someone else for the job," she said last week in Nevada.

Warren, however, provided a different account in a 2007 interview . In that conversation, she said after her first year working as a speech therapist for children with disabilities, she “went back to graduate school and took a couple of courses in education and said, 'I don’t think this is going to work out for me.’ And I was pregnant with my first baby, so I had a baby and stayed home for a couple of years.”

Records from 1971 Riverdale Board of Education meetings obtained by the Washington Free Beacon show that Warren’s contract was renewed in April 1971 and that she submitted a letter of resignation, accepted by the board “with regret,” in June 1971. Warren’s daughter, businesswoman Amelia Warren Tyagi, now 48, was born in September of that year.

Amid continued scrutiny of a DNA test that found she had a Native American ancestor six to 10 generations back, Warren has repeatedly apologized for making “mistakes,” doing so again as recently as this summer. But this time the senator is sticking to her version of events about being fired for being pregnant, even fundraising over the flap and building her email list by asking supporters to send in their own encounters with pregnancy discrimination.

"All I know is I was 22 years old, I was six months pregnant, and the job that I had been promised for the next year was going to someone else. The principal said they were going to hire someone else for my job,” Warren said this week. She told CBS News she wasn’t ready in 2007 to “open up” about the experience until after she was elected to the Senate in 2012.

Yet the revelations may not deter Democratic primary voters from backing Warren.

“How many administration officials have resigned after Trump showed them the door?” Murphy said. “It’s what usually happens in a professional position when you’re forced out.”

Daniella Gibbs Léger, Center for American Progress Action Fund’s executive vice president, said the anecdote was Warren's way of connecting with people on the campaign trial. Any criticism may be overshadowed by the possible impeachment of President Trump, she said.

“The fact that Sen. Warren is telling her very personal story could be helpful to her,” Gibbs Léger told the Washington Examiner. “Pregnancy discrimination is real, and something that women still face in 2019. That it happened to her in the early 70s can’t be shocking to any rational person, and it’s a story that is unfortunately relatable for many women.”