Donald Trump often gives the impression that he’d rather run against anyone else than Joe Biden. Trump’s stock in trade is venomous bigotry, so he has little to work with against Biden, a straight white Christian man and steadfastly middle-of-the-road Democrat. Trump’s preferred moniker for Biden (“Sleepy Joe”) suggests the problem: It’s hard to feel threatened by someone who is sleepy.

Much of Trump’s campaign rhetoric has been taken up with linking Biden with other politicians who are more easily attacked via racism, sexism, and anti-Semitism. To properly work up his followers, Trump needs to invoke the more active agents of evil like “Crooked Hillary” and “Crazy Bernie.” Trump has repeatedly suggested that Biden is just a stalking horse for figures like Kamala Harris, Bernie Sanders, Alexandria Ocasio-Cortez, Hillary Clinton, Nancy Pelosi, and Cory Booker. Lurking behind them all is the biggest devil in Trump’s personal demonology, Barack Obama.

Speaking in Lansing, Mich. on Tuesday, Trump predicted that if Biden is elected, he’ll be quickly replaced by Harris. “That’s why they’re talking about the 25th Amendment, right?” Trump asserted. “Three weeks. Three weeks in, Joe’s shot, ‘Let’s go Kamala, are you get ready?’” Some anti-Trump commentators mistakenly thought Trump was suggesting Biden would be shot, but the clear implication is that Biden would be physically and intellectually too frail to carry out the duties of his office.

The previous day in Lititz, Pa., Trump said, “Joe Biden has made a corrupt bargain in exchange for his party’s nomination. He’s handed control of his party over to the socialist, Marxists and left-wing extremists. And if Biden wins, the flag-burning radicals on the streets will be running your government.”

Trump’s decision to attack Biden’s associates rather than just Biden himself is a strategic mistake. It leads to diffuse and contradictory arguments. Historically, voters have only been marginally influenced by vice presidential candidates, let alone presidential allies. It’s the top of the ticket that counts, but Trump is all too quick to move the argument away from Biden.

Trump has never successfully defined Biden. Expanding the field of insults to include a pantheon of prominent Democrats only makes Trump’s argument even more incoherent.

Is Biden, as Trump sometimes suggests, the avatar of 47 years of failed policies that haven’t fixed any problems? Or is he the front man for a socialist revolution that will utterly transform America? Is Biden so doddering that he’s a few weeks away from handing over the presidency to Kamala Harris? Or is he the cunning mastermind behind an international crime family with tentacles in China and Ukraine?

Trump’s inability to focus on a clearly defined argument against Biden has created an opportunity for Biden’s surrogates. Because Trump is so eager to attack those around Biden, they have the opportunity to serve as effective distractions and foils. Every moment Trump focuses on attacking a Biden surrogate is a moment he’s failing at the essential task of drawing a contrast that makes him look better than Biden.

Of all of Biden’s surrogates, none has taken to the task of baiting Trump with quite as much glee as Obama. The Trump/Obama feud is of course of long standing. Much of Trump’s particular brand of racism seems to be fueled by resentment that a Black man was once a popular president. Trump built his base with the Republican right by championing birtherism. Obama famously humiliated Trump at the White House Correspondents’ Dinner of 2011 by making jokes at the real estate magnate’s expense. As if in revenge, Trump has been obsessively focused on tearing down Obama’s legacy with moves like withdrawing from the Paris climate accord and the Iran nuclear deal.

Over the last week, Obama has taken a more prominent role in being the foremost Trump goader. As Charles Pierce noted in Esquire, we are not seeing the familiar Obama who likes to elevate debate (the “Inspirational Obama, and Devotional Obama, and Better Angels Obama”) but rather “Snarkmaster Obama.”

This is an Obama who is openly incredulous that so unfit and buffoonish a figure as Trump should replace him. His voice dripping with scornful amazement, Obama has hammered home at Trump’s deep character flaws. Last Wednesday speaking in Philadelphia, Obama said:

I never thought Donald Trump would embrace my vision or continue my policies but I did hope for the sake of the country that he might show some interest in taking the job seriously, but it hasn’t happened. He hasn’t shown any interest in doing the work or helping anybody but himself and his friends or treating the presidency like a reality show that he can use to get attention. And by the way, even then his TV ratings are down. So you know that upsets him.

After the Philadelphia speech, Obama reportedly told a friend, “Oh man, that felt good.” Feeling he had hit the right note of derision, Obama was eager to do a repeat performance.

Obama returned to this theme the following Tuesday in a speech in Orlando, Fla., saying that Trump values the presidency as “a reality show that can give him the attention that he craves, and he does crave attention.”

In the Orlando speech, Obama also said:

If [Trump] had been focused on Covid from the beginning, cases wouldn’t be reaching new record highs across the country this week. If we were focused on Covid now, the White House wouldn’t be having its second outbreak in a month. The White House. Let me say this, I lived in the White House for a while. It’s a controlled environment. You can take some preventative measures in the White House to avoid getting sick, except this guy can’t seem to do it. He’s turned the White House into a hot zone.

Obama’s speeches are clearly getting under Trump’s skin. Less than an hour after Obama’s Philadelphia speech, Trump tweeted, “Nobody is showing up for Obama’s hate laced speeches. 47 people! No energy, but still better than Joe!”

On Monday, Trump told a rally, “Barack Hussein Obama showed up too. You know how many people he’s drawing at these rallies? He’s drawing flies, flies. 20, 30, 40. Not quite this crowd.” Trump then grumbled at the fact that Obama is considered a good speaker and handsome. Trump muttered that when Obama “gets up and then they say, ‘Oh, he’s so rhetorically good.’ I never thought he was a good speaker personally. I really never did. Then they say he’s so handsome. He’s so handsome. Oh, okay, he’s so handsome. He’s so handsome. Oh, okay. All right.”

Trump’s undisguised jealousy of Obama is not just squalid; it’s also a strategic mistake. Obama isn’t on the ballot. Whatever racial resentment Trump can stoke by going after Obama appeals only to voters already in Trump’s camp.

Trump needs to make the case against his actual rival. Compared to 2016, the polls in the Trump-Biden contest have been remarkably stable, almost like two parallel lines, with Biden since early June consistently 7 percent to 11 percent ahead of Trump. The lack of fluctuation has many causes, but one is that Trump really hasn’t made the effort to go after Biden.

Trump been content with fighting ghosts of previous battles. If Trump loses next week, one factor in his defeat will be that he can’t let go of his Obama obsession.