Democratic presidential candidate and former vice president Joe Biden in Berlin, N.H., on Tuesday. (Cj Gunther/EPA-EFE/Shutterstock)

Though former vice president Joe Biden is ahead of the crowded 2020 presidential field in every poll, his greatest vulnerability presents itself again and again: He is a man out of step with his party.

His record on crime has already put him at odds with the Democratic base, as has his praise of bipartisan compromise at a time when there is little appetite for appeasement. But Biden has proved surprisingly skillful at balancing the doubts that Democrats have about his record against a presumption that he might be their strongest bet to oust President Trump from the White House next year.

On Wednesday, Biden opened a new breach — this one potentially irreconcilable.

His campaign announced that the former senator and vice president continues to support the Hyde Amendment, a provision of federal law passed in 1976 that bars the use of federal funds for abortion services, except in rare cases.

The amendment — named for the conservative Illinois congressman, Henry J. Hyde, who initially sponsored it — stipulates that Medicaid, the program that provides health-care services to poor people, does not provide coverage of abortion, except in instances of rape, incest or a risk to the life of the mother. Before it was implemented, Medicaid paid for an estimated 300,000 abortions a year.

No surprise, Biden’s rivals for the nomination piled on, as did Democratic lawmakers and women’s groups. “Repealing the Hyde Amendment is critical so that low-income women in particular can have access to the reproductive care they need and deserve,” presidential candidate Sen. Kirsten Gillibrand (D-N.Y.) tweeted. “Reproductive rights are human rights, period. They should be nonnegotiable for all Democrats.”

For most of Biden’s career, his support for a ban on federal funding of abortion has put him well within the mainstream.

President Barack Obama straddled both sides of the question. In 2008, Obama campaigned on a promise to pass the Freedom of Choice Act, which would have effectively repealed the Hyde Amendment. Then, in 2010, he signed an executive order that enshrined Hyde, a deal he had to make to get the Affordable Care Act passed.

But that was then. In 2016, as it prepared to nominate a woman for president, the Democratic Party for the first time added a plank to its platform explicitly calling for the repeal of the Hyde Amendment.

The abortion issue has since gained more urgency with Democrats. Trump has made two conservative appointments to the Supreme Court, creating the potential that the landmark 1973  Roe v. Wade decision legalizing abortion could be overturned. Meanwhile, Republican-controlled state legislatures are passing a spate of highly restrictive laws designed to create the court challenge that could do just that.

With his party having swung so hard on the abortion issue, Biden’s isolation on the Hyde Amendment will no doubt revive other doubts about him with regard to gender-related matters. They include the recent flap over his clueless habit of putting his hands on women who come within reach, and the shabby treatment the Biden-chaired Senate Judiciary Committee gave to Anita Hill during the 1991 confirmation hearings of Justice Clarence Thomas.

Biden is far from the first presidential candidate to confront a political landscape that has shifted dramatically over the course of a long career.

Al Gore, the Democrats’ 2000 nominee, had to disavow as vice president some of the positions he had taken as a Tennessee congressman, including support for the tobacco industry and for lax gun laws. But doing so cast more doubt on Gore’s authenticity, which turned out to be one of his greatest handicaps.

So standing firm on the Hyde Amendment may perhaps pay off for Biden in the long run, as he looks toward a general-election contest against Trump. Polls have long indicated that while overturning the provision is popular among Democrats, most Americans are uncomfortable with providing federal funding for a medical procedure many regard as immoral.

Still, Biden has taken a stand that will undoubtedly make the going rougher as he heads into the first set of Democratic debates and will test his agility as a candidate. And that is not a small challenge for a candidate who has not run in his own right for more than a decade — and one who is not known for being sure-footed.

So now the question is whether this is really Biden’s party to lead or one that has passed him by.