Former Vice President Joe Biden on Thursday received a wave of congressional endorsements shortly after announcing his 2020 presidential campaign, highlighting his long tenure and relationships in Congress.

Biden, a Pennsylvania native who represented Delaware in the Senate for 36 years, nabbed four endorsements from Democratic senators: Chris Coons of Delaware, Tom Carper of Delaware, Bob Casey of Pennsylvania and Doug Jones of Alabama. Coons won a special election to replace Biden in 2009 when he became vice president.

"The quality that makes Joe stand out is his ability to bring people together to find common ground while standing up for what he believes is right," Jones tweeted Thursday. "We need to listen to each other & get things done for working people. Joe can, and will, do that. That's why I support Joe Biden."

Biden has so far received the largest number of endorsements from Democratic senators. The other Democratic candidates to receive endorsements from the Senate are all senators themselves, and have each received one endorsement from a colleague in their state. That list includes Sens. Elizabeth Warren of Massachusetts, Bernie Sanders of Vermont, Amy Klobuchar of Minnesota, and Cory Booker of New Jersey.

Biden also scored support from several House lawmakers, including Democratic Reps. Tom Suozzi of New York and Lisa Blunt Rochester of Delaware.

Early Thursday morning, Biden became the 20th candidate to enter the Democratic presidential primary, making it his third bid for the White House. He's viewed as a front-runner with a lead in most public polling, but questions have emerged about claims of inappropriate behavior as well as his record in a left-lurching primary.

Biden has been repeatedly labeled as a moderate. But he has rejected that label, noting that he was never described that way while running in any of his past races.

"The definition of progressive now seems to be changing," Biden told reporters in early April. "I'll stack my record on those things against people who are running or will run."

Former President Barack Obama also offered praise for Biden after his announcement, but stopped short of a formal endorsement.

"President Obama has long said that selecting Joe Biden as his running mate in 2008 was one of the best decisions he ever made," Obama spokeswoman Katie Hill said in a statement, according to The Associated Press. "He relied on the vice president's knowledge, insight, and judgment throughout both campaigns and the entire presidency. The two forged a special bond over the last 10 years and remain close today."

And President Donald Trump on Thursday tweeted about Biden's official announcement, mocking him as "Sleepy Joe."