Trump mentioned Biden so many times during the debate that Harris felt she needed to remind him he wasn't there

• Donald Trump mentioned Joe Biden more than a dozen times during Tuesday's debate.
• Vice President Harris felt compelled to remind Trump that Biden wasn't there.
• The former president's attacks on his successor were embelmatic of Trump's disjointed performance.

President Joe Biden watched Tuesday night's debate on TV like the rest of the nation, but if you listened to former President Donald Trump, it sounded like the president was standing on the stage across from him.

Trump's team telegraphed that he would repeatedly try to yoke Vice President Kamala Harris to Biden's unpopular record. Instead, the former president appeared rattled as he railed against an opponent who wasn't even in the same state.

According to ABC's official transcript, Trump mentioned Biden 14 times by name. He also referred to Harris' boss another four times. Trump just couldn't put to rest his fixation with the man he routinely called "Sleepy Joe."

Biden was, obviously, going to be part of the discussion. But how Trump attacked the president encapsulated his struggles to define Harris since Biden dropped out of the race following his disastrous June debate performance.

At one point, Trump took a question about how he would fight climate change and turned it into an attack on Hunter Biden, the president's son and the first child of a sitting president to face a criminal trial. Harris had nothing to do with the president's son's business practices since most of the allegations center on Biden's vice presidency when Harris was in California.

"He's afraid to do it. Between him and his son. They get all this money from Ukraine. They get all this money from all of these different countries," Trump said. "And then you wonder why is he so loyal to this one, that one Ukraine, China? Why is he? Why did he get 3 1/2 million dollars from the mayor of Moscow's wife? Why did he get -- why did she pay him 3 1/2 million dollars? This is a crooked administration, and they're selling our country down the tubes."

Republicans have never directly proved Biden benefited from his son's business deals which was the central premise of a monthlong impeachment inquiry . The GOP is quietly killing off that probe with the possibility that there might not even be a formal floor vote. Instead, Republicans have pivoted to trying to probe Minnesota Gov. Tim Walz, Harris' running mate.

Trump couldn't even decide how to attack Harris in the context of Biden. He claimed that the president "hates her." He said Biden is the "worst president," then he said that Harris would be even more worse. Toward the end, he settled on the line that Harris, a 59-year-old woman of color, actually is Biden.

"She is Biden," he said. "She's trying to get away from Biden. I don't know the gentleman, she says. She is Biden."

Harris felt compelled to remind viewers that the rematch polls showed voters long loathed was in fact not happening.

"Clearly, I am not Joe Biden, and I am certainly not Donald Trump," she said.

Trump's meandering attacks underlined an even bigger problem with his performance: He constantly mentioned the past. After months of Republicans begging him to stop talking about 2020, Trump couldn't even bring himself to repeat his own recent statement that he lost to Biden "by a whisker."

"Are you now acknowledging that you lost in 2020?" ABC News moderator David Muir asked.

Trump replied: "No, I don't acknowledge that at all."

Before Muir reminded him, "But you did say that."

Harris seized on Trump's compulsion for history. She was far more consistent in hammering home her theme that she represents a departure from the status quo, despite the fact that she's currently in power.

"We're not going back. It's time to turn the page," Harris said when talking about the Capitol riot. "And if that was a bridge too far for you, well, there is a place in our campaign for you."