There were just a handful of goals for Trump, a source familiar with the debate prep told RCP:

Knock Biden off his talking points by answering questions from moderator Chris Wallace of Fox News and then posing another one to his opponent. Force him to own up to the less popular parts of his own record. Push the centrist Democrat to own the policy agenda of those on his left flank.

“The more Joe stutters and stumbles and makes mistakes and says things that just don’t resonate or make sense,” the source told RCP the day before the debate, “the more we’re winning.”…

Much of the debate was wasted with this kind of jawboning, and little policy was actually discussed in detail. But as Trump was trying to peg Biden as a radical, he only succeeded in chasing the Democrat to the center. The Green New Deal? Biden said he didn’t support it. Rioting in the streets? Biden condemned violence. Defunding the police? Biden said he would increase funding. Just as Republicans struggled to define Biden over the summer, Trump was all over the place throughout the night. His punches didn’t land as hard as they did four years ago, and his new opponent was not as easily demonized as Hillary Clinton. But the president never stopped interrupting, which at some point became the issue itself.