One of Joe Biden's biggest selling points as a presidential candidate is the residual glow he enjoys from his time as vice president to Barack Obama. New Jersey senator Corey Booker even called him out for it during the first round of presidential debates, saying, "You invoke President Obama more than anybody in this campaign. You can’t do it when it’s convenient and then dodge it when it’s not."

But despite Biden and Obama's relationship being largely rosy, "Mr. Biden’s simmering ambition was a source of unease for both men," according to the New York Times, which published a deep dive into their history on Friday. The story contains some moments of Biden being characteristically odd, like one instance in 2013 when Senate majority leader Mitch McConnell said he wouldn't support any budget deal with the White House before his upcoming reelection campaign. Biden responded to the man who early on vowed to stonewall as much of Obama's agenda as possible, "Mitch, we want to see you come back."

The most surprising part of the Times story though is how Obama has on multiple occasions tried to dissuade Biden from running for president. First, in 2016, Obama pressured Biden to sit out the race because he believed Hillary Clinton was the best shot at continuing his legacy. Even though that didn't pan out for Obama, he still tried to talk Biden out of running in 2020. Per the Times:

The two men spoke at least a half dozen times before Mr. Biden decided to run, and Mr. Obama took pains to cast his doubts about the campaign in personal terms."You don’t have to do this, Joe, you really don’t," Mr. Obama told Mr. Biden earlier this year, according to a person familiar with the exchange. Mr. Biden — who thinks he could have defeated Donald Trump four years ago—responded by telling Mr. Obama he could never forgive himself if he turned down a second shot at Mr. Trump.

Since announcing his candidacy, Biden has proven himself exceptionally gaffe-prone, repeatedly referring to former British prime minister Theresa May as Margaret Thatcher, claiming he was vice president during the 2017 high school shooting in Parkland, Florida, and saying, "Poor kids are just as bright, just as talented, as white kids," at a speech in Iowa. Apart from making verbal stumbles, he's also defended his working relationship with segregationists in Congress.

The Times also reports that in March, Obama summoned Biden's top campaign advisers, Anita Dunn and Kate Bedingfield, to his Washington office. Multiple sources confirmed to the Times that the ex-president warned the advisers to make sure that Biden doesn't "embarrass himself" or "damage his legacy."