text:  Perhaps the biggest moment came early in the debate when Biden appeared to lose his train of thought while answering a question about tax cuts. ABC's Andrew Timbert, ABC's Mary Bruce, says many Democrats are seriously questioning Biden's performance this morning. They know this was a very bad night for the president, and they are well aware of this wave of panic that we are now seeing from Democrats. But they insist and argue that, look, this was just one night, that this race was never going to be determined in a single debate. And they are adamant that they are not going to change course.