As he sets off for a busy fall campaign schedule, Joe Biden hasn't been shy about backing candidates facing challenges from the progressive left. In two of the remaining primaries this month, New York and Delaware the former vice president is backing incumbents and close allies over challengers with support from leading progressive forces.

In a new television advertisement released days after Andrew Cuomo's feisty debate with progressive primary opponent Cynthia Nixon, Biden calls the two-term New York governor "the perfect antidote" to the "challenging times" facing the nation under President Trump.

"I've known Andrew for over 20 years. I know he has skills, guts and experience -- experience to defend New York against the conservative agenda coming out of Washington," he says. "We need Andrew's experience more than ever to make sure that everybody gets a fighting chance."

Though he could have been a potential 2020 rival to Biden, Cuomo seemed to rule out a presidential run during that debate last week. He said he would serve all four years of a third term unless "God strikes me dead."

Biden and Cuomo have forged a close relationship especially in the past decade. The former vice president long admired Cuomo's father, Mario, and partnered with his son to announce major new infrastructure projects in the state like a new La Guardia Airport. The younger Cuomo also had become close with Biden's eldest son, Beau, when both served as their respective states' attorneys general.

Biden also endorsed his home-state senator, Tom Carper, ahead of his primary this week.