President Joe Biden had been facing growing pressure from his own party to step aside from the 2024 race, despite his repeated assurances that he plans to stay in the race.

Pressure had mounted after his disastrous June debate with former President Donald Trump which left many within the Democratic Party questioning if he could win his reelection campaign. Before he made his announcement, at least 40 congressional lawmakers had publicly called on Biden to step aside.

Biden's decision Sunday -- which came as he recovers from COVID-19 -- took members of his staff by surprise, despite his repeated assurances doing little to decrease public pressure for him to step down.

President Joe Biden had conversations with the two top congressional Democrats Sunday as he ended his 2024 presidential campaign, sources told ABC News.

Biden spoke with Senate Majority Leader Chuck Schumer and House Minority Leader Hakeem Jeffries, sources said.

U.S. Secretary of Homeland Security Alejandro Mayorkas weighed in on Biden's decision to end his bid for reelection Sunday.

"Today and everyday, it is an honor to serve under POTUS Biden’s leadership," Mayorkas said in a statement on X.

Mayorkas said he's "extraordinarily proud" of the work the Department of Homeland Security has done to "secure our shores, skies, borders, and cyberspace; safeguard the American people from threats old and new; and advance our vital homeland security mission under the President’s leadership."

Looking to the future of Biden's tenure as president, Mayorkas said, "We will continue to use every minute of this administration to deliver for the American people."

After Harris announced her intention to join the 2024 race for president, anti-abortion rights groups released a statement criticizing Harris' support of abortion rights. National Right to Life, a major anti-abortion group, released a statement criticizing Harris, calling her "radically pro-abortion" after Harris announced she will be running for president.

"Kamala Harris is radically pro-abortion and sees the lives of precious unborn babies as expendable ... She has toured the country pushing unlimited abortion and criticizing protective state laws that support women and their preborn children," National Right to Life President Carol Tobias said in a statement.

Susan B. Anthony Pro-Life America, which opposes access to abortion care, also accused her of refusing to support limits on access to abortion care.

"While Joe Biden has trouble saying the word abortion, Kamala Harris shouts it. In contrast, President Trump, JD Vance, and the GOP reject the Democrat attempt to impose abortion on-demand across all 50 states and support the right of states to place limits on abortion," Susan B. Anthony Pro-Life America President Marjorie Dannenfelser wrote in a statement.