Following the first round of debates for the Democratic primaries, can Joe Biden, the initial runaway favorite, still count on votes from African Americans to win the race? According to the blows dealt by fellow candidate Kamala Harris, nothing could be less certain.

They say that if a tree falls in a forest and there is no one around to hear it, then it didn’t make a sound. Conversely, when a presidential candidate screws up in a live debate watched by 15 million people, the moment is less likely to go unnoticed. But that is the general consensus, among both analysts and the general public, developing the day after Joe Biden’s below average performance in the first Democratic debates last week.

Biden’s lead for the position of Democratic presidential candidate, which at the launch of his candidacy in May was 25 points ahead of his nearest rival, has been cut by around a half because of his missteps, particularly regarding public financing of abortion. But two new national surveys for CNN and Quinnipiac University published earlier this week indicate that the lead really has disintegrated. It is now no more than two and five points respectively ahead of his closest competition, Californian Sen. Kamala Harris.

Harris has dominated headlines for her tough attack on Biden during the debate on the question of racial desegregation during the 70s. While a young senator, Biden opposed federal busing of white children to schools in black neighborhoods and vice versa. Although extremely controversial at the time, for a Democratic candidate in 2019, the idea has become politically indefensible.

The issue is even more prickly for Biden, considering that Harris is herself black and that Biden’s lead up to this point was anchored first and foremost by his strong position with African American voters. Biden’s lead with these voters, more than 30 points ahead, has been reduced in CNN and Quinnipiac’s surveys to two and 10 points.

It is important to be aware of the weight that these voters have in the Democratic primaries. In the race between Hillary Clinton and Bernie Sanders in 2016, African Americans made up around a quarter of Democratic voters nationwide. Among white voters, Clinton and Sanders were on equal footing, but what allowed Clinton to outstrip her rival was basically that she picked up slightly more than three-quarters of the black vote, dominating inordinately, compared with Sanders.

Clinton swept several Southern states which was a huge factor in catapulting her toward the party nomination. In South Carolina, a key state because it votes early in the primary calendar, Clinton won 86% of the black vote. In Georgia, she won 85% with 91% in Mississippi and 93% in Alabama. In each case, black voters made up an absolute majority in the Democratic electorate and they are expected to do the same in 2020.

It is not, therefore, a coincidence that Harris has chosen a racial issue over any other to launch her first salvo in the debate against Biden. Nor is it a coincidence that the following day, Biden tried to limit the damage by flying to Chicago, the city where Barack Obama started his political career and where nearly a third of the inhabitants are black, to give a speech to leaders of the African American community. The act seemed like a tribute to the president, the first African American in American history, of course, who Biden served as vice president from 2009 to 2017.

It is not first time that Biden has tried to play his Obama connection to boost his own presidential ambitions. Only last month, he posted a strange, at best, picture of a friendship bracelet with the names “Joe” and “Barack” to highlight “Best Friends Day.”

This approach is not without risk for Biden, though. After all, Obama has never supported Biden’s candidacy. This is remarkable in itself, considering that the last two Democratic vice presidents to launch a presidential campaign, Walter Mondale, vice president to Jimmy Carter in 1984, Al Gore, vice president to Bill Clinton in 2000, were able to count unequivocally on the public support of the presidents they had served from the start of the primaries.

For his part, in 2016, Obama actively discouraged Biden from setting his sights on the White House to leave the way clear for Hillary Clinton. Then, earlier this year when Biden faced a barrage of criticism for his allegedly inappropriate behavior toward several women, Obama did not come out even once to defend the integrity or reputation of his vice president.

If the best safeguard which Biden can pin his hopes on when it comes to protecting his lead among African American voters is his loyal service to Obama, the question his opponents, whether Harris or others, will want to ask him at future debates is patently obvious: “Why doesn’t Obama return the favor?”

It remains to be seen if Biden’s defense will be more convincing than the one he came up with the first time his support from voters was attacked.