The 1976 Hyde Amendment prohibits the use of Medicaid funds for most abortions. Biden, who voted as a senator in favor of the Hyde Amendment when it was first written, had reaffirmed his support for the law often, most recently on Wednesday.

Biden's former support for the Hyde Amendment had prompted many other Democratic candidates for president to announce their support for federally-funded abortions. The Democratic Party's 2016 platform includes a call for the public funding of abortions.

Before Thursday evening's switch, Biden had supported some aspects of pro-life legislation during his political career. In addition to his Senate vote in favor of the Hyde amendment, he also supported the Mexico City Policy in 1984, voted again in favor of Hyde in 1993, and voted to ban partial-birth abortion in 1995 and 1997.

In an interview shortly after the 1973 Roe v. Wade decision, Biden refused to support unrestricted access to abortion and said that he thought the Supreme Court "went too far" in their decision. In 1981, he lent his name to the "Biden Amendment," which bans the use of federal funds for biomedical research involving abortion or involuntary sterilization.

By 2012, in the vice presidential debate against then-Rep. Paul Ryan (R-WI), Biden described himself as being personally pro-life, though he also expressed his support for legally protecting abortion.
Biden is Catholic and has spoken publicly about his faith.

At the time the Hyde Amendment was signed into law in 1977, it had the support of nearly half of Congressional Democrats. Nationally, more than half of Americans say they do not support federal funding of abortions.

While three out of four women who undergo abortions are living in poverty, the Hyde Amendment is actually far less popular among low-income voters. A 2016 poll found that only 24 percent of people making under $25,000 a year said they were in favor of the public funding of abortion services, compared to 45 percent of people making over $75,000.

Biden's abrupt about-face on the Hyde Amendment has let down pro-life Democrats, who were once hopeful that Biden would break the party mould on abortion.

"We are extremely disappointed that Vice President Biden choose to cave to the pressure of the abortion lobby instead of standing with a majority of Americans who support the Hyde Amendment," Kristen Day, the executive director of Democrats for Life of America, told CNA.

"With all the major candidates fighting to be the most extreme on abortion, there is a wide open lane for a candidate to bring an alternative position to the discussion and to unify Democrats around common ground principles," she added.

Day said that Democrats should instead work for equal opportunity and equality, instead of paying for abortions for poorer women.

"Poor women don't want money for abortions; they want the same opportunities to parent as their rich counterparts."