Trump tweeted in support of Pence saying he is, "doing GREAT" and Harris, calling her a "gaffe machine," a criticism he uses often to attack her running mate Joe Biden.

Biden has also tweeted in support of his running mate during the debate, saying that Harris is "showing the American people why I chose her as my running mate."

In speaking to American leadership, Pence brought up the case of Kayla Mueller, a humanitarian worker from Arizona who was kidnapped by the Islamic State in Syria in 2013 and died in the terror group's custody.

Mueller's parents were in the debate's audience as Pence's guests and appeared last month at the Republican National Convention.

Pence suggested former President Barack Obama and Biden carried blame for Mueller's death, saying they "hesitated for a month" while she was held captive.

Harris, in her response to the topic of American leadership, first addressed Mueller's family.

"First of all, to the Mueller family, I know about your daughter's case and I'm so sorry. I'm so sorry. What happened to her is awful and it should have never happened," Harris said. "And I know Joe feels the same way. And I know that President Obama feels the same way."

In a discussion of foreign policy and the role of American leadership, Harris brought up Trump’s handling of the Iran nuclear deal and criticized the president's “unilateral” approach.

“He's walked away from agreements,” she said. “We were in the Iran nuclear deal with friends, with allies around the country. And because of Donald Trump's unilateral approach to foreign policy, coupled with his isolationism, he pulled us out and has made America less safe.”

“So, Susan, it's about relationships and the thing that has always been part of the strength of our nation, in addition to our great military, has been that we keep our word,” she added. “But Donald Trump doesn't understand that because he doesn't understand what it means to be honest.”

On the issue of jobs, Harris took aim at the Trump administration trade policy with China.

“You lost that trade war. You lost it. What ended up happening is because of a so-called trade war with China, America lost 300,000 manufacturing jobs,” Harris said. “Farmers have experienced bankruptcy because of it. We are in a manufacturing recession because of it.”

Pence responded by criticizing Joe Biden’s record on China, calling him, “a cheerleader for communist China.”

“When Joe Biden was vice president, we lost 200,000 manufacturing jobs and President Obama said they were never coming back,” Pence said.

Pence pivoted from a question on pre-existing conditions to press Harris for an answer on whether or not she and Biden supported adding additional seats to the Supreme Court.

"I think the American people would really like to know, if Judge Amy Coney Barrett is confirmed to the Supreme Court of the United States, are you and Joe Biden, if somehow you win this election, going to pack the Supreme Court to get your way?" the vice president asked.

Harris used her first answer to attack the Trump administration for rushing a vote on Barrett's nomination by bringing up a Republican the president often compares himself to -- Abraham Lincoln.

"It was 27 days before the election, and a seat became open on the United States court. Abraham Lincoln's party was in charge of not only the White House but the Senate," she said, referring to the 1864 election.

"But Honest Abe said it's not the right thing to do," Harris added. "The American people deserve to make the decision about who will be the next president of the United States, and then that person can select who will serve for a lifetime on the highest court of our land. And so, Joe and I are very clear: the American people are voting right now, and it should be their decision about who will serve on this most important body for a lifetime."

MORE: Most say wait on Ginsburg seat, while opposing packing the court: Poll

Pence used her non-answer to say that Biden and Harris would pack the Supreme Court and that he and Trump would protect the current number of justices on the court. 
"The American people deserve a straight answer," he said. "And if you have not figured it out yet, the straight answer is they are going to pack the Supreme Court, if they somehow win this election.

Harris responded that Republican efforts to get more conservatives confirmed as federal judges amounted to packing the court, noting that of the 50 people the president nominated to the Court of Appeals none were Black. She did not state her position on adding seats to the U.S. Supreme Court.