Former Vice President Joe Biden to announce he's entering the 2020 race Thursday

ABC News has confirmed that former Vice President Joe Biden will announce he's entering the 2020 race Thursday morning in a video.

It will mark Biden's third run for the presidency and he'll enter the crowded Democratic field at the top of several polls.

Biden brings a long career in public service to his presidential bid, which began in 1972 when he was elected to the Senate in Delaware. Biden served in the Senate for nearly 40 years, where he was chairman of the Senate Judiciary and Foreign Relations committees, before becoming vice president in 2009.

Biden is likely to face scrutiny for some of his past policy positions including his anti-bussing legislation in the 1970s, his role in the 1994 crime bill and his handling of the Anita Hill hearings as chairman of the Judiciary committee.

Biden has taken steps to acknowledge these past issues ahead of his run. During a speech on Martin Luther King Jr. Day, Biden said the country needs to do more to acknowledge the racism built into 'every aspect of our system."

Biden also acknowledged his role in 1980's drug legislation that disproportionally hurt minorities by creating longer mandatory minimum sentencing for crack cocaine than powder cocaine.

"It was a big mistake when it was made. We thought we were told by the experts that crack -- you never go back; it was somehow fundamentally different. It's not different," he said. "But it's trapped an entire generation," Biden said at the National Action Network's MLK breakfast in January.

In March, Biden spoke about his role in Anita Hill's testimony during Supreme Court Justice's Clarence Thomas' confirmation hearings.

"To this day, I regret I couldn't come up with a way to get her the kind of hearing she deserved," Biden said, while speaking at the Biden Courage Awards, an event to honor students who've intervened to prevent sexual assault.

New controversies could also provide a challenge to Biden's candidacy, including some women who say that Biden made them feel uncomfortable in past interactions by touching them without their permission.

Biden posted a video acknowledging that 'social norms are changing' and promising he would be "much more mindful," calling it his "responsibility."

Biden first ran for president in 1988 but dropped out of the race just a few months later after reports of plagiarism arose. Biden used elements of a speech by a British politician as his own, without attribution. In an interview with ABC News, Biden explained the scandal as "Stupid. My mistake. Born out of ignorance, thinking I didn't have to prepare."

The former vice president also sought the 2008 Democratic nomination, dropping out after receiving less than 1% of the vote in the Iowa Caucus, and failing to win any delegates.

ABC News' Kendall Karson and Christopher Donato contributed to this report.