Former Vice President Joe Biden is one of the top candidates in the race for the Democratic presidential nomination, representing a moderate option in a field with democratic socialist Sen. Bernie Sanders, I-Vt., and hardline progressive Sen. Elizabeth Warren, D-Mass., among the front-runners.

Here are five things to know about Biden as the 2020 presidential election cycle is officially underway.

1. He's been in Washington longer than some of his competitors have been alive

Biden, born less than a year after the United States entered World War II, is among four septuagenarians – along with Warren, Sanders and former New York City Mayor Mike Bloomberg – competing for the Democratic nomination. He was first elected as a U.S. senator from Delaware at 29 years old in 1972 (he turned 30 by the time he was sworn in).

Biden's election came three years before businessman Andrew Yang was born, nine years before U.S. Rep. Tulsi Gabbard of Hawaii was born, and 10 years before former South Bend Mayor Pete Buttigieg was born.

2. His previous presidential campaigns haven't gone very well

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Biden's most recent run for president was in 2008. While then-Sen. Barack Obama was making history with his major win in Iowa, Biden garnered just 0.8 percent of the vote to finish in dead last.

Biden, however, reached higher office than any of the other also-rans, with Obama choosing him to be vice president.

Biden also campaigned for president in 1988 but withdrew before a single vote was cast amid accusations of plagiarism.

3. He's landed in hot water in the past for apparent personal space issues

Biden has a habit of getting very physically close to people, particularly women and children, while making public appearances. As Biden was rolling out his campaign last year, former Democratic candidate for Nevada lieutenant governor Lucy Flores said Biden put his hands on her shoulders, smelled her hair, and kissed her on the back of her head in 2014 at a campaign event. And former congressional staffer Amy Lappos alleged that Biden grabbed her head and neck and touched noses, expressing that she thought he was going to kiss her on the mouth at a fundraiser in 2009.

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He's also been called out for poking voters asking him questions in the chest, talking about children rubbing his leg hair and biting his wife's finger on stage at a campaign event.

Last year Biden defended himself against accusations of unwanted touching, saying "social norms have begun to change ... and the boundaries of protecting personal space have been reset," while promising to be more mindful of them.

4. His campaign calls his long record on human rights 'unassailable'

After a June debate in which Sen. Kamala Harris, D-Calif., attacked Biden for working with Southern senators during his early years in Washington, the Biden campaign went into overdrive defending his record.

"If you want to put Vice President Biden’s record on civil rights up against anybody else on that stage, he’ll stand the test of time," campaign adviser Symone Sanders told reporters in the spin room of the debate.

Biden, a longtime senator and the vice president to the first African-American president in U.S. history, touts his work on the Violence Against Women Act, the Hate Crimes Prevention Act, same-sex marriage, the Employment Non-Discrimination Act and more on his campaign website.

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5. He's a big train guy

When he was a Delaware senator, Biden would commute between Wilmington, Del., and Washington, D.C., on Amtrak almost every day. The Amtrak station in Wilmington is named after him.

Biden secured $1.3 billion for Amtrak in Obama's 2009 stimulus bill and his son, Hunter, previously sat in an unpaid seat on the board of Amtrak. The younger Biden was nominated to the position in 2006 by then-President George W. Bush.

Fox News' Joseph A. Wulfsohn, Brooke Singman and Vandana Rambaran contributed to this report.