Former New York City Mayor Michael Bloomberg (26 percent) and former Vice President Joe Biden (25 percent) were the most likely beneficiaries of the false perception that Obama had endorsed someone. The effect was mirrored among people who said they voted for Obama in 2012 and heightened among black voters, who were more likely than others to say Obama was backing a candidate.

An endorsement from Obama would likely be a game-changer for any of the candidates, throwing the weight of the party’s most popular figure (with a 90 percent favorability rating among Democratic primary voters as recently as December) behind their campaign at a key moment. A Morning Consult poll in October found 73 percent of Democratic voters said they would be more likely to vote for a candidate backed by Obama, more than other figures tested.

According to a source in touch with the former president, Obama is reluctant to put his thumb on the scale, viewing an endorsement as potentially divisive in the current contest and limiting his ability to help unite the Democratic Party around an eventual nominee to defeat President Donald Trump in November.