Joe Biden wanted to save the “soul of America” from Donald Trump, but his stubborn defiance of the march of time may have cleared his rival’s path back to power.

Biden caved in to growing pressure Sunday and announced he is dropping out of the presidential race, amid concerns over his mental acuity and ability to beat Trump and serve four more years.

As he fought for his political survival after a disastrous debate, the 81-year-old Democrat repeatedly cited his family’s mantra that “when you get knocked down, get back up again.”