This piece by Traister is definitive, but I would particularly like to highlight this part:

A young Joe Biden was reliably anti-abortion, claiming that Roe v. Wade “went too far” and that he did not believe that “a woman has the sole right to say what should happen to her body.” He voted consistently for the Hyde Amendment, the 1976 legislative rider which forbid government-funded insurance programs from paying for abortion, making abortion all but inaccessible to poor people. In 1981, he proposed the “Biden Amendment,” prohibiting foreign aid to be used in any biomedical research related to abortion. The next year, he supported Jesse Helms’s amendment barring foreign NGOs receiving United States aid from using that aid to perform abortion. Biden was one of two Democrats on the Senate Judiciary to vote for the 1982 Hatch Amendment, which would have effectively nullified Roe by turning abortion rights back to federal and state legislatures. At the time, he expressed concern about whether he had “a right to impose” his anti-abortion views on the nation. Then he went ahead and imposed those views anyway. Over the decades, Biden has evolved on the issue, yet into the 1990s and 2000s, he voted for the so-called “Partial-Birth Abortion Ban Act.” And he regularly declined to fully support the Freedom of Choice Act, which would have banned the wide variety of oppressive state restrictions on abortion. Biden’s stances against women’s full reproductive freedom have been key to how he has proudly presented himself to the public. Even in the years since he has officially become pro-choice, he’s retained the sensibility first reflected in his comments about how women shouldn’t be wholly in charge of their own decisions, writing in his 2007 memoir that even though he’d vote against a constitutional amendment barring abortion, “I still vote against partial birth abortion and federal funding, and I’d like to make it easier for scared young mothers to choose not to have an abortion.” His is the language of restrictive authority dressed up as avuncular protectionism.

Some of the bad parts of Biden’s record have at least partially mitigating context — any senator from Delaware is going to be too friendly to the financial services industry, the Clinton crime bill had far broader support within the party than people like to pretend now, his position in the Hill hearings was undermined by the fact that the most prominent Democratic senator on the committee (inter many alia) had literally left a woman to drown to save his own political career, etc. There’s no particular reason to want someone with this record as your presidential nominee in 2020 when there are multiple superior alternatives, but OK. On abortion, however, he started out terrible and continued to be well to Bill Clinton’s right while representing a completely safe seat. This in itself should be disqualifying for a Dem nominee in 2020.

One would hope that after the Lucy Flores story and the reaction to it Biden has figured out this isn’t how he wants his political career to end, but ego is a hell of a drug.